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PubMed1992

Right heart function during prosthetic left ventricular assistance in a porcine model of congestive heart failure.

A left ventricular assist device was used to produce a 90% reduction in peak systolic left ventricular pressure in pigs with congestive heart failure, and the resultant effects on right ventricular function were determined. Initially, eight farm pigs underwent rapid ventricular pacing at 230 beats/min for 7 days to produce congestive heart failure. When compared with an independent series of normal pigs, cardiac output in the paced animals was 33.3% less (2.2 +/- 0.2 versus 3.3 +/- 0.5 L/min; p less than 0.05), left ventricular end-diastolic pressure was elevated (13.8 +/- 3.5 versus 6.6 +/- 1.8 mm Hg; p less than 0.05), and the slope of the right ventricular global stroke work curve was significantly depressed (0.004 +/- 0.001 versus 0.033 +/- 0.003 joules/mm Hg; p less than 0.05). Next, the left ventricular assist device was connected between left ventricular apex and ascending aorta and left ventricular pressure was reduced from 92.0 +/- 3.8 to 10.5 +/- 2.2 mm Hg, while systemic arterial pressure was maintained constant. This led to a further impairment in cardiac output (-14%), mean arterial pressure (-15%), and the slope of the right ventricular global stroke work curve (-50%). Under each condition, right ventricular preload recruitable stroke work and end-systolic pressure-dimension relationships were studied in three different regions on the right ventricle during both steady-state and transient inferior vena caval occlusion. In the right ventricular septal-free wall dimension, left ventricular pressure unloading resulted in a 47.5% +/- 5.4% (p less than 0.05) reduction in the slope and 20.1% +/- 4.8% (p less than 0.05) increase in the dimension intercept of the preload recruitable stroke work relationship. There was also a 44.6% +/- 4.8% (p less than 0.05) reduction in the slope and 15.6% +/- 2.8% (p less than 0.05) increase in the dimension intercept of the end-systolic pressure-dimension relation. These slope changes plus reductions in cardiac output and in global stroke work, which are indicative of impaired right ventricular function during left ventricular pressure unloading in the congestive heart failure pigs, are not seen in normal hearts, whereas the intercept changes associated with leftward septal shift are present in both. These results suggest that anatomic ventricular interactions have a more significant role in heart failure than in the normal heart in determining overall right ventricular function during left ventricular assist device support.

Animals↗
PubMed2004

Pathogenesis of cigarette smoke-induced chronic obstructive pulmonary disease and therapeutic effects of glucocorticoids and N-acetylcysteine in rats.

BACKGROUND: T lymphocytes and matrix metalloproteinase (MMP) play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the details of the mechanisms involved are unclear. The aims of this study were to investigate the changes in interferon-gamma (IFN-gamma), interleukin-4 (IL-4), MMP-9, MMP-12 and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels in a smoke-induced COPD rat model and the therapeutic effects of glucocorticoids and N-acetylcysteine. METHODS: Male Wistar rats were exposed to cigarette smoke for 3.5 months. Budesonide or N-acetylcysteine was given in the last month. Lung function was measured at the end of the study. IL-4 and IFN-gamma levels were then determined in bronchoalveolar lavage fluid and lung tissue samples by enzyme-linked immunosorbent assay. The expression of MMP-9, MMP-12 and TIMP-1 mRNA in lung tissue was determined by RT-PCR. RESULTS: In comparison with the control group, rats exposed to smoke had a significant increase in IL-4 and MMP-12 levels and a significant decrease in IFN-gamma levels. In addition, the IL-4/IFN-gamma ratio and MMP-12/TIMP-1 ratio were both higher. At the same time, the ratio of forced expiratory volume in 0.3 second to forced vital capacity (FEV(0.3)/FVC) and dynamic compliance (C(dyn)) decreased and expiratory resistance (Re) increased. By measuring pulmonary mean linear intercept and mean alveolar numbers, obvious emphysematous changes were observed in the smoke exposed group. After treatment with budesonide, IL-4 and MMP-12 decreased and IFN-gamma increased. The IL-4/IFN-gamma ratio returned to normal, though the MMP-12/TIMP-1 ratio remained unchanged. FEV(0.3)/FVC was significantly higher and Re was significantly lower than that in untreated smoke exposed rats. No significant differences were found in pulmonary mean linear intercept and mean alveolar numbers. After treatment with N-acetylcysteine, IFN-gamma increased and the IL-4/IFN-gamma ratio decreased. The MMP-12/TIMP-1 ratio remained unchanged. Re and C(dyn) both improved obviously. No significant differences were found in pulmonary mean linear intercept and mean alveolar numbers. Correlation analysis indicated that IL-4 levels in lung tissue correlated negatively with FEV(0.3)/FVC (r = -0.53, P = 0.001), IFN-gamma levels in lung tissue correlated negatively with Re (r = -0.63, P = 0.000) and positively with C(dyn) (r = 0.44, P = 0.009), and that the IL-4/IFN-gamma ratio correlated negatively with FEV(0.3)/FVC (r = -0.44, P = 0.010) and C(dyn) (r = -0.42, P = 0.015) and positively with Re (r = 0.58, P = 0.000). Finally, MMP-12 correlated negatively with FEV(0.3)/FVC (r = -0.36, P = 0.026). CONCLUSIONS: Cigarette smoke exposure increases IL-4 levels and decreases IFN-gamma levels. This may be the result of smoke-induced changes in lung function. Budesonide can mitigate the changes in IL-4 and IFN-gamma levels induced by smoke exposure. N-acetylcysteine has no effect on IL-4, but increases IFN-gamma levels and brings the IL-4/IFN-gamma ratio back to normal. Cigarette smoke can also promote MMP-12 gene expression and elevate the MMP-12/TIMP-1 ratio. This effect may play a role in smoke-induced emphysema. Budesonide and N-acetylcysteine do not alter the MMP-12/TIMP-1 ratio in this study when given in the late phase of smoke exposure.

Acetylcysteine↗
PubMed2005

Myocardial compliance was not altered after acute induction of atrial fibrillation in sheep.

BACKGROUND: Although left ventricular (LV) contractility in atrial fibrillation (Af) is known to change in a beat-to-beat fashion, little is known about the changes in LV compliance in Af. MATERIAL/METHODS: We experimentally induced tachycardic Af (average heart rate - 154 beats per minute) in 18 sheep. LV volume and pressure were simultaneously monitored using a conductance catheter. LV end-diastolic volume (V(ED)) and pressure (P(ED)) were plotted in a beat-to-beat fashion and fitted to the following exponential equation (P(ED)=gamma x e(b x V(ED))) in each animal. A random effects model was constructed to determine if the intercepts and slopes differ. RESULTS: In all animals, those plots after the induction of Af fit quite well to the exponential function (r=0.834+/-0.184) by gating short preceding interval (RR1) beats. By simply taking the natural logarithm of both sides in the equation, the linear relationship (ln(P(ED)) =alpha+ betaxV(ED), where a = lng) was observed in all animals before (normal sinus rhythm, NSR) and after the induction of Af. Only two of 18 intercepts and four of 18 slopes deviate between NSR and Af. Most interestingly, the random effects model clearly detailed that the average animal had intercepts and slopes that were not discernibly different between NSR and Af. CONCLUSIONS: Unlike LV contractility, myocardial compliance did not change after the acute induction of Af. These interesting results may give us insights into the understanding of the physiology in acute rapid Af.

Animals↗
PubMed2006

Geographic variation in alcohol, drug, and mental health services utilization: what are the sources of the variation?

BACKGROUND: Studies have documented geographic variation in health services utilization over a range of medical, surgical, and psychiatric conditions. These geographic differences are of concern to policy makers, as they may represent either excessive levels of unnecessary care or inappropriately low utilization of necessary services. However, the sources of geographic variation are not well understood, and variation may not represent a quality problem, to the extent that geographic variation is due to sampling variability or variation in case-mix across sites. AIMS OF THE STUDY: Our aim was to determine the extent to which geographic variation in assessment and treatment rates for alcohol, drug, and mental disorders (ADM) was due to variation in case-mix across sites and to quantify the amount of geographic variation after case-mix adjustment. METHODS: We analyzed data from Healthcare for Communities, a nationally representative telephone survey of ADM disorders and treatment. We utilized fixed effects and random intercept models to analyze whether individuals received a brief primary care ADM assessment, any primary care ADM treatment, any specialty ADM treatment, or any ADM treatment. Using the coefficient of variation and intra-class correlation (ICC) as summaries, we simulated reference distributions for the amount of variability in ADM assessment and treatment rates expected due to variation in case mix across 60 geographic areas. We compared this with the actual variation among our 60 sites, and the variation that remained after adjusting for ADM disorders, physical health, and socioeconomic characteristics. RESULTS: The amount of the variation in assessment and treatment rates explained by geographic area in unadjusted fixed effects and random intercepts models was statistically significant with R2 statistics ranging from 1% to 2% in fixed effects models and ICC's ranging from 0.009 to 0.043. Considerably more variation was explained in analyses that included individual level characteristics such as ADM disorders, physical health, and socioeconomic status, with R2 statistics from 10% to 19%. In random intercept models the ICC's were decreased 20 to 100% in models that adjusted for ADM disorders, physical health, and socioeconomic status. DISCUSSION: We found significant variation in ADM assessment and treatment rates across geographic sites. However, the magnitude of geographic variation was relatively modest, with 0.9 to 4.3% of the total variation in ADM assessment and treatment occurring at the geographic level. Further, it appears that a moderate amount of this geographic variation may be due to differences in case mix across sites. IMPLICATIONS FOR HEALTH POLICY: Although geographic variation in assessment and treatment rates can signal variable quality, there may be only modest potential for improving quality by reducing geographic variation. Further, the success of efforts to decrease geographic variation by focusing on provider behavior may be limited by the extent to which systematic variation is explained by individual characteristics. IMPLICATIONS FOR FURTHER RESEARCH: Future work on geographic differences in mental health care as well as in health services more generally should pay particular attention to adjusting for individual differences in morbidity, which strongly predict treatment utilization.

Adolescent↗
PubMed1991

Calibration of Technicon Chem 1 multitest analysers.

Recently, two Technicon Chem 1 multitest clinical chemistry analysers were introduced after an evaluation in our laboratory. Calibration according to the instructions of the manufacturer resulted in significant differences between the assay results of the two Chem 1 analysers for twelve of twenty-two methods. To remove these differences we used an additional procedure based on the NCCLS EP-9P protocol for method comparison. Four reference methods were used as comparison methods. Our results indicate that, for three of these methods, the results on both Chem 1 analysers are biased in slope and intercept, and corrections of these parameters are necessary to produce results comparable to the reference method values. For the remaining eighteen assays, methods in routine use in our laboratory were used as comparison methods. In fifteen of eighteen assays, corrections of slope and (or) intercept were necessary to prevent changes in the cumulative average patient data produced by our laboratory. An adjustment of the slopes and intercepts, according to the multi-point calibration procedure presented here, resulted in significant differences between system-specific values measured in our laboratory and those assigned by the manufacturer for ten of thirteen methods. We conclude that the use of the multi-point calibration procedure presented in this article (based on calibration according to the instructions of the manufacturer and NCCLS EP-9P) greatly improves the intra-laboratory comparability and therefore should be part of multi-centre evaluations.

Autoanalysis↗
PubMed1978

The lung of the copper-deficient rat. A model for developmental pulmonary emphysema.

Based on the hypothesis that cross-linked elastin is critical for normal lung structure, lung tissue from copper-deficient rats was studied. Copper deficiency was induced in the second generation by feeding dams a milk-based diet low in copper (less than 1 ppm) during gestation and lactation. The weanlings were fed the same diet until they showed severe signs of deficiency between 6 and 10 weeks of age. Controls animals received the basal diet supplemented with 10 ppm copper. Liver cytochrome oxidase activity, which served as the chief index of deficiency, decreased from a normal level of approximately 80 to 15 mumole/min/g. The lungs of the deficient animals contained 17% less elastin and had 35% larger alveolar spaces (34.7 vs 47.7 intercepts), as determined by the mean alveolar intercept method. The ultrastructure of elastin in the bronchi, arterioles, and alveolar ducts had a "washed out" appearance. To determine the reversibility of the pathology, deficient animals, 5 to 10 weeks of age, were repleted by feeding a copper-supplemented diet for 1, 2, and 3 months. During this period growth resumed, anemia disappeared, and liver cytochrome oxidase returned to normal. There was no improvement in lung structure with regard to alveolar size (28.4 intercepts compared with 43.6 in controls and 35.1 in deficient littermates killed at the start of repletion). The ultrastructure and electron density of pulmonary elastin was restored to near normal. The lung of the copper-deficient rat is proposed as a model for developmental pulmonary emphysema.

Animals↗
PubMed1990

Neuromuscular and cardiovascular effects of mivacurium chloride (BW B109OU) during nitrous oxide-narcotic, nitrous oxide-halothane and nitrous oxide-isoflurane anesthesia in surgical patients.

One hundred seventeen adult surgical patients were studied to compare neuromuscular and cardiovascular effects of mivacurium chloride during nitrous oxide-narcotic (BAL, n = 45) nitrous oxide-halothane (HAL, n = 27) and nitrous oxide-isoflurane (ISF, n = 45) anesthesia. Anesthesia was maintained with nitrous oxide (60%-70%) and oxygen (30%-40%) with end-tidal concentrations of halothane or isoflurane to yield a total MAC of approximately 1.25, or with supplemental fentanyl and thiopental as clinically indicated. Twitch response of the adductor pollicis muscle was elicited by supramaximal square wave pulses of 0.2 msec duration at a frequency of 0.15 Hz (Grass S44 stimulator) to the ulnar nerve and quantitated by a Grass FT10 transducer. Nine patients in each of the HAL and ISF groups received one of four doses of mivacurium (0.03, 0.05, 0.10 or 0.15 mg/kg). Ninety patients in the balanced anesthesia group received one of seven doses of mivacurium (0.03, 0.04, 0.05, 0.08, 0.15, 0.20, 0.25 mg/kg). The ED50, ED75 and ED95 of mivacurium in each group were estimated from linear regression plots of log dose versus probit of maximum percentage depression of twitch height. The ED50, ED75 and ED95 for halothane and isoflurane are 0.040, 0.053 and 0.081 and 0.037, 0.043 and 0.053, respectively. The ED50, ED75, and ED95 for the balanced group are 0.039, 0.050, and 0.073 mg/kg respectively. There was no significant difference between the slopes of the HAL and BAL inhalation anesthetic dose-response curves. The slope of the ISF group was significantly than the slope of the BAL group. Intercepts of the HAL and BAL curves were not different. The isoflurane curve's intercept was significantly less than the other groups' intercepts, lying above the halothane curve, but below the BAL curve. For the 0.05 mg/kg dose, maximum block was greater in the ISF group (89.1 +/- 2.7%, n = 9) than in the HAL (70.3 +/- 7.6%, n = 9) or BAL (67.7 +/- 6.4%, n = 9) groups. At higher doses of mivacurium, isoflurane produces a greater potentiation of neuromuscular block than halothane or balanced anesthesia. There were no significant cardiovascular changes seen in any group following mivacurium doses up to 0.15 mg/kg (approximately 2xED95).

Adult↗
PubMed1990

Importance of the mitral subvalvular apparatus for left ventricular segmental systolic mechanics.

The relative importance of the anterolateral (ANTLAT) and posteromedial (POSTMED) papillary muscle (PM) chordae tendineae for left ventricular (LV) segmental wall function was assessed in 12 in situ ejecting canine hearts. Pairs of piezoelectric crystals were placed in the regions subtending PM insertions and the ANTLAT LV free wall to measure wall thickness. After mitral valve replacement with complete preservation of the subvalvular apparatus, chordal attachments to either the ANTLAT PM or POSTMED PM were randomly severed using exteriorized snares, followed by subsequent division of the remaining chordae tendineae. Segmental wall function in each region was determined at each stage by segmental preload recruitable stroke work (sPRSW, slope of the segmental stroke work-end-diastolic wall thickness relation). The order in which the chordae were severed was unimportant (p greater than 0.530 in all regions). When the ANTLAT PM chordae were severed first, there were significant declines in sPRSW without a change in the wall thickness intercept in both the ANTLAT (-71.0 +/- 18.3 vs. -57.7 +/- 16.8 mmHg, p less than 0.05) and POSTMED (-81.8 +/- 23.1 vs. -65.4 +/- 17.3 mmHg, p less than 0.05) PM insertion sites. No further significant reductions in sPRSW in either region were detected after severing the remaining chordal attachments to the POSTMED PM. sPRSW in the ANTLAT LV free wall decreased progressively, reaching statistical significance when both sets of chordae tendineae were divided (-88.3 +/- 14.3 vs. -74.0 +/- 15.2 mm Hg, p less than 0.05). When the POSTMED PM chordae were severed first, no significant changes in sPRSW or the wall thickness intercept in either region of PM insertion were detected. Subsequent division of the ANTLAT PM chordal attachments reduced sPRSW significantly in both the ANTLAT PM (-65.9 +/- 21.1 vs. -56.1 +/- 22.1 mm Hg, p less than 0.05) and POSTMED PM (-78.8 +/- 24.7 vs. -67.2 +/- 24.0 mm Hg, p less than 0.05) insertion sites, without a shift in the wall thickness intercept. In the ANTLAT LV free wall, sPRSW again fell progressively, achieving statistical significance only when both chordal attachments were severed (-78.6 +/- 14.8 vs. -62.2 +/- 13.7 mm Hg, p less than 0.05). In conclusion, division of the chordae tendineae resulted in a decline in segmental LV function not only in the areas subtending PM insertions but also in remote LV regions. Furthermore, the influence of the ANTLAT PM chordae predominated local LV systolic function at both PM insertion sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Pancreatic amylase measured in serum by use of a monoclonal antibody immunochemically immobilized to a solid phase.

We studied a method for measuring the pancreatic isoenzyme of amylase (EC 3.2.1.1) by use of a mouse monoclonal antibody against human salivary-type amylase (Clin Chem 1985;31:1283) coupled indirectly to particles of polyvinylidene fluoride via polyclonal goat anti-mouse immunoglobulin. These particles, in 200 microL of a suspension, could remove salivary amylase (activity 2200 U/L) from an equal volume of serum in 5 min. Measurement of amylase activity in the supernatant fluids from treated sera thus provided an assay of pancreatic amylase. Precision studies at three activity concentrations yielded within-run CVs of 1.6% to 1.7% (n = 25) and total CVs of 2.2% to 5.1% (20 days). Salivary amylase added to each of 10 sera was completely (99.8%, SD 1.6%) removed. The new method (y) showed the following regression statistics when compared with an electrophoretic method (x): slope = 0.989 (SD 0.019), intercept = -0.220% (SD 1.48%), SEE 4.0%, n = 51. Similar respective regression values were found for urine samples: slope = 0.934 (SD 0.053), intercept = 2.3 U/L (SD 3.2), SEE 8.4 U/L, n = 26. The following respective values were found when the new method (y) was compared with the previously described immunoprecipitation assay (x): slope = 1.02 (SD 0.02), intercept = 2.2% (SD 1.4%), SEE 3.3%, n = 23 sera. Reference intervals for pancreatic amylase activity in serum were established for three different substrates: maltotetraose, maltopentaose, and p-nitrophenylheptaoside.

Acute Disease↗
PubMed1986

Electrical and mechanical train-of-four responses during depolarizing and nondepolarizing neuromuscular blockade.

Simultaneous measurements of train-of-four (TOF) responses by integrated electromyography (IEMG) and twitch force were compared for atracurium, vecuronium, and succinylcholine in 30 subjects during nitrous oxide-fentanyl anesthesia. Determinations of TOF were made during neuromuscular blockade (NMB) onset and recovery. Scattergrams and least squares regression lines were plotted, and z-tests for parallel slope and common intercept were used to compare lines. Data for atracurium and vecuronium were indistinguishable in all groups (z less than 0.05), and therefore pooled to represent nondepolarizing blockade. During onset of nondepolarizing NMB, TOF showed a linear relationship indistinguishable from the line of identity (slope 0.93, intercept -0.06, z less than 0.05). During recovery the intercept was unchanged (z greater than 0.05), but the slope was significantly changed, indicating mechanical TOF lags behind IEMG during recovery. This finding is important for interpretation of IEMG when used for clinical monitoring. Comparison of data for depolarizing NMB shows more complex relationships. Integrated electromyography is found to be convenient and reliable for monitoring nondepolarizing NMB.

Adult↗
PubMed1977

Mechanism of T5-induced DNA polymerase. I. Replication of short primer templates.

Bacteriophage T5-induced DNA polymerase shows an initial phase of rapid synthesis, followed by a slower steady rate for much longer periods, with short DNA primer-templates (400 to 600 nucleotides long), in vitro. On extrapolating the line of steady rate back to 0 min, an intercept is obtained on the ordinate. With large DNA primer-templates, such as denatured T5 DNA (average chain length approximately 50,000 bases), the rate of synthesis remains constant and is equal to the initial rate obtained with short primer-templates. The zero time intercept was proportional to the amount of enzyme used and independent of temperature. Polymer challenge experiments indicate that the initial phase of rapid synthesis can be attributed to the processive mode of synthesis by T5 DNA polymerase. After synthesizing a stretch of DNA processively for about 200 nucleotide residues, the enzyme apparently forms a "dead-end complex" with the primer-templates used and must dissociate from the primer-template in order to resume synthesis. The average size of the product made processively, during various phase of synthesis, remains invariant and is in good agreement with the size of the zero time intercept per enzyme molecule.

Coliphages↗
PubMed1978

Characteristics of statistical parameters used to interpret least-squares results.

This paper discusses properties of several statistical parameters that are useful in judging the quality of least-squares fits of experimental data and in interpreting least-squares results. The presentation includes simplified equations that emphasize similarities and dissimilarities among the standard error of estimate, the standard deviations of slopes and intercepts, the correlation coefficient, and the degree of correlation between the least-squares slope and intercept. The equations are used to illustrate dependencies of these parameters upon experimentally controlled variables such as the number of data points and the range and average value of the independent variable. Results are interpreted in terms of which parameters are most useful for different kinds of applications. The paper also includes a discussion of joint confidence intervals that should be used when slopes and intercepts are highly correlated and presents equations that can be used to judge the degree of correlation between these coefficients and to compute the elliptical joint confidence intervals. The parabolic confidence intervals for calibration cures are also discussed briefly.

Chemistry, Clinical↗
PubMed1983

Pharmacokinetic study of neomycin in calves following intravenous and intramuscular administration.

Neomycin sulfate was administered to calves by the intravenous and intramuscular routes. Serum drug levels were determined and the intravenous pharmacokinetic parameters derived using the Gauss-Newton nonlinear fitting algorithm and the two compartment open model. The kinetic parameters determined were as follows: zero time intercept, serum drug level 68.045 +/- 15.894 micrograms/mL, alpha slope intercept 37.666 +/- 13.874 micrograms/mL and beta slope intercept 30.379 +/- 12.638 micrograms/mL; equilibration rate (pool I and II) 0.081 +/- 9.064 min-1; elimination rate 0.004 +/- 0.001 min-1; half-time alpha 14.774 +/- 11.236 min, half-time beta 166.596 +/- 47.576 min; first order elimination constant 0.009 +/- 0.002 min+; transfer rate constants, central to peripheral, 0.032 +/- 0.026 min+ and peripheral to central 0.045 +/- 0.037 min-1; volume of central compartment 0.186 +/- 0.047 L/kg; volume of distribution 0.388 +/- 0.130 L/kg; body clearance 0.002 +/- 0.001 L/kg/min.

Animals↗
PubMedDate not supplied

Improved expiratory airflow dynamics with smoking cessation.

Lung recoil, Pst(1), dependence and gas density dependence of maximum expiratory flow (Vmax) using air and an 80% helium + 20% oxygen (HeO2) gas mixture before and 60 +/- 4 (means +/- SD) days after cessation of smoking were determined in five male and five female subjects (33.4 +/- 6.4 years). Pst(1) dependence of Vmax, a relationship dependent on airway elastance at the "choke", was estimated by measuring the slope and the zero flow intercept using the maximum flow-static recoil (MFSR) curve. MFSR slope was unchanged by abstinence. The intercept showed no difference between air and HeO2 before or after cessation of smoking. Density independence of the zero flow intercept is deducible from wave speed theory if there is no change at the "choke" and the slope truly reflects the elastic behaviour of the "choke". This correspondence of theory and measurement suggests that the "choke" was not changed by abstinence. The reduction of Pst(1) with smoking cessation, without any fall in Vmax at the same lung volume, suggests a complementary reduction in lung recoil and frictional energy loss upstream of the "choke". This would suggest that a decrease in small airway muscle tone was the single cause of a reduction of Pst(1) and peripheral airway resistance.

Adult↗
PubMed1981

Estimation of very-low-density lipoprotein cholesterol from data on triglyceride concentration in plasma.

We examined the relationship in a large-living population between the concentration of triglycerides in plasma from fasting persons and the concentration of very-low-density lipoprotein cholesterol (VLDL-C) as determined after preparative ultracentrifugation. Data from individuals in the Framingham Heart Study who were free of coronary heart disease, did not have Fredrickson Type I, III, or V hyperlipoproteinemia, and whose plasma-triglyceride values were less than 4000 mg/L were considered in the analyses. A total of 4100 Framingham Offspring, ages 20-49 years, met these criteria, as did 2284 participants in the original Framingham Cohort, aged 50-79 years. We estimated a linear regression model with an intercept and slope coefficient, using VLDL-C (units, mg/L) as the dependent variable and triglycerides as the dependent variable. The intercept was approximately 30.0 mg/L, and the slope coefficient for triglycerides was about 0.20 when all age and sex groups were combined. However, when the analysis was performed by age group, the slope coefficient for triglycerides increased with each age group only for women. The model, in which a different intercept and slope is used for each age and sex group was statistically better than a previously developed simpler model. On the other hand, the older model, in which VLDL-C is easily estimated by multiplying the triglyceride value by 0.20, is reasonably accurate and is very simple to use. The generalizability of the model is discussed in the light of results from other population studies.

Adult↗
PubMed1982

Radioimmunoassay and lipid-chromatographic analysis for free cortisol in urine compared with isotope dilution--mass spectrometry.

I compared results by three different routine methods for analysis for urinary cortisol with those by a highly specific reference method based on isotope dilution--mass spectrometry (i). A "high-performance" liquid-chromatographic method (II) gave the most comparable results (regression coefficient 0.86, intercept 9 nmol/L). For some urines much lower values were obtained by I than by II. Two radioimmunoassay (III) methods, one involving direct assay and one involving extraction, gave less-accurate results (regression coefficients of 1.87 and 1.52 and intercepts of 86 and 12 nmol/L, respectively, although values obtained by III and by I correlated well (r = 0.95-0.99), indicating a relation between the free cortisol and the compounds interfering in III. The apparent accuracy for the extraction method was previously assayed by I (regression coefficient 0.90, intercept 6 nmol/L). All four methods investigated showed a statistically significant sex-related difference in 24-h urinary cortisol excretion; evidently such a finding should be a prerequisite in any such method proposed for routine use.

Adult↗
PubMed1982

Reaction time and mild mental retardation: high speed scanning reexamined.

When observers judge whether a probe is contained within a small positive set, reaction time (RT) increases linearly with set size (Sternberg, 1969b). Slope and intercept of the function relating RT to positive set size are believed to reflect durations of different processing stages. As results of several investigations suggested inverse slope/intercept relationships, however, studies using "high-speed scanning" tasks to compare retarded with nonretarded individuals were reexamined. When slope was correlated with points along the RT function (intercept, Positive Set Sizes 1, 2, and 4), results showed no interdependencies for nonretarded adults. Slope and intercept were negatively correlated for retarded and nonretarded adolescents, whereas slope and Positive Set Size 1 values apparently were unrelated. These results seem to contradict theoretical expectations, and specification of processing stages where efficiency varies across populations may not be possible based on results from high speed scanning tasks.

Adolescent↗
PubMed1981

Computer-based calibration of the DuPont ACA II.

Desk-top computers equipped with 16K memory and programmed in BASIC can be used to produce calibration calculations for the DuPont ACA II. Entries are made by the operator in accordance with the ACA-supplied calibration format and results may be displayed on a video screen and/or programmed for hard copies to be produced by the use of an interfaced line printer. The operator is provided with the option of computing the Y-intercept from a hand-drawn graph, or allowing the computer to calculate it from the slope. The final printout supplies the averages necessary for plotting the calibration curve, slope and intercept of the line, new intercept, new starting point, and new scale factor. The calibration involved on the ACA II is time-consuming and frequently may produce mathematical errors, both of which are eliminated by the use of the described computer program.

Calibration↗