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At least 793 records · Page 44Linked to original sources
PubMed1988

Assessment of extruded grain amaranth as a feed ingredient for broilers. 2. Apparent amino acid availability values.

Apparent amino acid availabilities (AAAA) were determined for grain amaranth in two experiments using broilers. Total collection method (TCM) and acid-insoluble ash (AIA), as a marker, were used for these determinations. Individual amino acid availabilities for the extruded grain were calculated both by regression analysis and by difference from the basal diet. From the linear regression equations, TCM produced more accurate results than did the AIA method, based on standard errors of the intercept and coefficient of determination. Predicted AAAA, based on linear regression equations, from the TCM were 92.4, 79.9, and 89.4% for methionine, lysine, and arginine, respectively. Using the TCM and calculation by difference, average AAAA on an as-fed basis were 85.0, 79.1, and 92.9% for methionine, lysine, and arginine, respectively. The AAAA of 11 other amino acids were also determined.

Amino Acids↗
PubMed1994

Excimer laser ablation rate and corneal hydration.

During excimer laser photorefractive keratectomy, dehydration of the cornea begins as soon as the epithelium is removed. Corneal hydration might affect the excimer laser ablation rate, which could affect the accuracy of correction. We studied the effect of corneal hydration on the excimer laser ablation rate in bovine eyes. To control hydration, bovine corneoscleral rims were equilibrated in dextran solutions of varying concentrations. One button trephined from each rim underwent laser ablation. Hydrated tissue ablation rates (amount of collagen, ground substance, and water removed per pulse) and dry component ablation rates (amount of collagen and ground substance removed per pulse) were calculated from mass removed. The hydrated tissue ablation rate at physiologic hydration was 0.40 micron/pulse. As corneal hydration increased, the hydrated tissue ablation rate increased by 5.6 micrograms/cm2/pulse per increase in unit corneal hydration (simple linear regression analysis, P = .0001). The dry component ablation rate decreased linearly by 0.82 microgram/cm2/pulse per unit increase in corneal hydration (simple linear regression analysis, P = .0001). Both clinical data and theoretical arguments imply that dry component ablation rate determines refractive outcome after photorefractive keratectomy. Since the dry component ablation rate increases as the cornea dries, significant dehydration of the cornea before ablation might lead to relative overcorrections of myopia. Surgeons should use a technique that minimizes changes in hydration to maximize the predictability of excimer laser photorefractive keratectomy.

Animals↗
PubMed1998

Canadian semen quality: an analysis of sperm density among eleven academic fertility centers.

OBJECTIVE: To determine whether sperm quality has declined among Canadian men during the past 13 years and whether there are regional differences in sperm quality. DESIGN: Retrospective temporal series of cross-sectional studies. SETTING: University fertility centers across Canada. PATIENT(S): Men being investigated as part of the normal infertility work-up. MAIN OUTCOME MEASURE(S): Sperm concentrations among all the samples were compared on an annual basis to assess any changes over 13 years from 1984 through 1996. RESULT(S): There were regional differences and trends in both up and down directions. Linear regression analysis of the means of each center for each year showed no significant trend. However, when all the samples were analyzed by regression analysis there was a significant downward trend. CONCLUSION(S): Linear regression analysis showed a significant downward trend in sperm concentration among 48,968 samples from Canadian men obtained from 1984 through 1996. A significant difference was seen in the mean concentrations between centers, ranging from 48.6 to 104.5 X 10(6)/mL. Secular trends in sperm density are dependent on the statistical method used for analysis.

Canada↗
PubMed1988

A mechanistic and kinetic analysis of the interactions of the diastereoisomers of adenosine 3',5'-(cyclic)phosphorothioate with purified cyclic AMP-dependent protein kinase.

The binding affinities of the diastereoisomers of adenosine 3',5'-(cyclic)phosphorothioate, Sp-cAMP[S] and Rp-cAMP[S], for the cyclic AMP- (cAMP-)binding sites on purified and reconstituted pig heart type II cAMP-dependent protein kinase holoenzyme were determined by measuring the ability of these compounds to displace [3H]cAMP from this enzyme. Sp-cAMP[S], a cAMP agonist, displaced 50% of the [3H]cAMP bound to the holoenzyme at a concentration 10-fold higher than that of cAMP; Rp-cAMP[S], a cAMP antagonist, required a 100-fold higher concentration relative to cAMP. Activation of the isolated holoenzyme, determined as phosphotransferase activity, was measured in the presence of the agonist and in the absence and in the presence of increasing concentrations of the antagonist. The results of fitting the activation data to sigmoid curves with a non-linear-regression program and to Hill plots by using a linear-regression program showed that Rp-cAMP[S] had no effect on Vmax, increased the EC50 values for agonist activation and had no effect on the co-operativity of activation (h). A Ki value of 11 microM was determined for Rp-cAMP[S] inhibition of cAMP-induced activation of purified type II cAMP-dependent protein kinase. Electrophoresis of the holoenzyme on polyacrylamide gels under non-denaturing conditions in the presence of saturating concentrations of the diastereoisomers resulted in 100% dissociation of the subunits with Sp-cAMP[S] and 0% dissociation with Rp-cAMP[S]. Sp-cAMP[S], the isomer with an axial exocyclic sulphur atom, binds to the holoenzyme, releases the catalytic subunit and activates the phosphotransferase activity. Rp-cAMP[S], the isomer with an equatorial exocyclic sulphur atom, binds to the holoenzyme but does not result in dissociation, and thus acts as a competitive inhibitor of phosphotransferase activity.

Animals↗
PubMed2001

Comparison of echocardiography with technetium 99m-gated single photon emission computed tomography as diagnostic tools for left ventricular ejection fraction.

Left ventricular ejection fractions (LVEF) are routinely measured and result in critical decision-making algorithms in cardiology. This study was conducted to compare the accepted standard two-dimensional (2-D) echocardiogram ejection fraction (EF(ECHO)) with single photon emission computed tomography rest ejection fraction (EF(SPECT)). Data were acquired and analyzed from 51 inpatients. EF(ECHO) was obtained using modified Simpson's rule in the four-chamber apical view, and gated EF(SPECT) was computed by an automated method (Siemens ICON software). Comparison between EF(ECHO) and EF(SPECT) was done by linear regression, Bland-Altman, and receiver operator characteristic (ROC) analyses. Linear regression analysis revealed EF(SPECT) = 1.12 x EF(ECHO) - 3.6%, r = 0.93, n = 51, P < 0.0001. Bland-Altman analysis showed that the limits of 95% confidence for the difference between EF(SPECT) and EF(ECHO) were - 12% to 18%. Ninety-eight percent of the datapoints were within the limits of confidence. The ROC analysis showed that the sensitivity and specificity for detecting abnormal EF (< or = 50%) were 85% and 86% with EF(SPECT), and 91% and 90% with EF(ECHO). This study showed good correlation as well as agreement between SPECT and two-dimensional echocardiograms in measuring EF.

Coronary Artery Disease↗
PubMed2004

Predicting thermal displacements in modular tool systems.

In the last decade, there has been an increasing interest in compensating thermally induced errors to improve the manufacturing accuracy of modular tool systems. These modular tool systems are interfaces between spindle and workpiece and consist of several complicatedly formed parts. Their thermal behavior is dominated by nonlinearities, delay and hysteresis effects even in tools with simpler geometry and it is difficult to describe it theoretically. Due to the dominant nonlinear nature of this behavior the so far used linear regression between the temperatures and the displacements is insufficient. Therefore, in this study we test the hypothesis whether we can reliably predict such thermal displacements via nonlinear temperature-displacement regression functions. These functions are estimated first from learning measurements using the alternating conditional expectation (ACE) algorithm and then tested on independent data sets. First, we analyze data that were generated by a finite element spindle model. We find that our approach is a powerful tool to describe the relation between temperatures and displacements for simulated data. Next, we analyze the temperature-displacement relationship in a silent real experimental setup, where the tool system is thermally forced. Again, the ACE algorithm is powerful to estimate the deformation with high precision. The corresponding errors obtained by using the nonlinear regression approach are 10-fold lower in comparison to multiple linear regression analysis. Finally, we investigate the thermal behavior of a modular tool system in a working milling machine and again get promising results. The thermally induced errors can be estimated with 1-2 microm accuracy using this nonlinear regression analysis. Therefore, this approach seems to be very useful for the development of new modular tool systems.

Computer Simulation↗
PubMed1994

Low-level lead exposure and renal function in the Normative Aging Study.

Occupational and environmental lead exposure has been associated with significant impairment in renal function. The authors studied the cross-sectional relation between creatinine clearance and blood lead concentration in a population of 744 men participating in the Normative Aging Study of the Department of Veterans Affairs between July 1988 and April 1991. These men, aged 43-90 years, were recruited from communities in the Greater Boston, Massachusetts, area and were selected without regard to lead exposure. The mean values for blood lead concentration and creatinine clearance rate were 8.1 micrograms/dl (standard deviation, 3.9 micrograms/dl) and 88.2 ml/minute (standard deviation, 22.0 ml/minute), respectively. Independent relations of creatinine clearance to blood lead were assessed by multivariate linear regression analysis, with adjustment for various potential confounders. In multivariate linear regression models, the rate of creatinine clearance was significantly and negatively associated with increasing levels of blood lead, even after adjustment for age, body mass index, and use of diuretic and analgesic medications (the beta-coefficient for ln blood lead measured in microgram[microgram/dl]-1 was -0.030; standard error = 0.014, p = 0.037). A rise in ln blood lead of 10.0 micrograms/dl was associated with a decrease in the ln creatinine clearance rate of 10.4 ml/minute. These results support the hypothesis that exposure to low-level environmental lead correlates with a significant decrement in renal function.

Adult↗
PubMed1985

Relationship between arterial and heated skin surface carbon dioxide tension in adults.

Carbon dioxide tension was measured on heated skin surface (PSCO2) and in arterial blood (PaCO2) in eight adult patients during intermittent positive pressure ventilation. A total of 299 PaCO2-PSCO2 measurements were performed at electrode temperatures of 45 degrees C, 43 degrees C and 38 degrees C. The PSCO2-PaCO2 relation was evaluated using: 1) linear regression, 2) PSCO2/PaCO2 ratio and 3) temperature correction methods. Both linear regression and ratio indicate temperature dependency of the PSCO2-PaCO2 relation. The temperature correction method was done with a blood PCO2 temperature coefficient of 4.6% per degrees C and at two temperatures: electrode temperature (according to Severinghaus) and estimated capillary blood temperature. The results indicate that the relation between PaCO2, PSCO2 and electrode temperature is constant enough to permit estimation of PaCO2 from PSCO2 during stable circulatory conditions.

Adult↗
PubMed1997

Nocturnal urinary 6-sulphatoxymelatonin excretion is decreased in primary breast cancer patients compared to age-matched controls and shows negative correlation with tumor-size.

In previous studies a tumor-size dependent decline of the circadian amplitude of serum melatonin was found in primary unoperated breast cancer patients, which was not due to changes of the hepatic metabolism of melatonin since its main peripheral metabolite, 6-sulphatoxymelatonin (aMT6s), showed similar serum levels. The aim of the current study was to verify these previous results by measurements of the nocturnal excretion of aMT6s in urine. The determination of aMT6s was carried out by radioimmunoassay. 17 primary unoperated breast cancer (BC) patients and 34 age-matched control patients with different types of benign gynecological diseases awaiting operation (breast diseases, n=13; ovarian diseases, n=12; and uterine diseases, n=9) were analysed. The median nocturnal urinary aMT6s excretion (22:00-6:00 hr) was significantly lower (-48%, P = 0.033) in BC patients than in controls. Controls showed a significant negative linear regression with age (r = -0.419, P = 0.014). According to multivariate linear regression analysis, BC revealed no age-dependency but a significant negative effect of increasing tumor-size on aMT6s-excretion (P = 0.036) was detected. These results confirm previous findings of a decreased pineal melatonin secretion in BC patients as well as an inverse relationship with tumor-size excluding a possible distortion due to age. The mechanisms involved are unknown but indicate that BC may lead to an impaired production of pineal melatonin. The clinical relevance of these findings from therapeutic and diagnostic point of view is discussed.

Breast Neoplasms↗
PubMedDate not supplied

Is there a link between the variation in gastric cancer mortality and differences in Helicobacter pylori prevalence in different regions of France?

An ecological study was performed to correlate the cumulative gastric cancer mortality rate to the prevalence of Helicobacter pylori infection in France. National data on mortality, standardized for age and gender, and the results of a nationwide prevalence study on Helicobacter pylori infection among 1,586 patients consulting for symptoms other than upper digestive tract symptoms, in seven defined French regions were used. The correlation was described by linear regression with the standardized data and then evaluated in a linear regression model including age and gender as co-variables. The Southwest region was the least affected by the infection (15.2%) while prevalence varied from 20.5 to 25.3% for the other regions. The cumulative gastric cancer mortality rate varied from 34.4 to 51.8/100,000. The prevalence of Helicobacter pylori infection in the model explained 5% of the variability in the gastric cancer mortality. A number of biases which were difficult to control could explain the lack of association between these variables.

Adolescent↗
PubMed2001

Simultaneous measurement of regional cerebral blood flow by perfusion CT and stable xenon CT: a validation study.

BACKGROUND AND PURPOSE: Knowledge of cerebral blood flow (CBF) alterations in cases of acute stroke could be valuable in the early management of these cases. Among imaging techniques affording evaluation of cerebral perfusion, perfusion CT studies involve sequential acquisition of cerebral CT sections obtained in an axial mode during the IV administration of iodinated contrast material. They are thus very easy to perform in emergency settings. Perfusion CT values of CBF have proved to be accurate in animals, and perfusion CT affords plausible values in humans. The purpose of this study was to validate perfusion CT studies of CBF by comparison with the results provided by stable xenon CT, which have been reported to be accurate, and to evaluate acquisition and processing modalities of CT data, notably the possible deconvolution methods and the selection of the reference artery. METHODS: Twelve stable xenon CT and perfusion CT cerebral examinations were performed within an interval of a few minutes in patients with various cerebrovascular diseases. CBF maps were obtained from perfusion CT data by deconvolution using singular value decomposition and least mean square methods. The CBF were compared with the stable xenon CT results in multiple regions of interest through linear regression analysis and bilateral t tests for matched variables. RESULTS: Linear regression analysis showed good correlation between perfusion CT and stable xenon CT CBF values (singular value decomposition method: R(2) = 0.79, slope = 0.87; least mean square method: R(2) = 0.67, slope = 0.83). Bilateral t tests for matched variables did not identify a significant difference between the two imaging methods (P >.1). Both deconvolution methods were equivalent (P >.1). The choice of the reference artery is a major concern and has a strong influence on the final perfusion CT CBF map. CONCLUSION: Perfusion CT studies of CBF achieved with adequate acquisition parameters and processing lead to accurate and reliable results.

Adult↗
PubMed2006

Do admissions data and NBDE Part I scores predict clinical performance among dental students?

The purpose of this study was to evaluate possible associations between a variety of measures used to evaluate didactic knowledge and clinical performance within a predoctoral dental program. In this study, clinical performance was assessed by clinical productivity and clinical proficiency across four different competency areas: operative dentistry, major restorative dentistry, fixed prosthodontics, and removable prosthodontics. Predental and preclinical predictors were undergraduate GPAs (overall and science), DAT subtest scores (including the Perceptual Ability Test, PAT), and performance on subtests of Part I of the National Board Dental Examination. The sample consisted of eighty-four students at the Harvard School of Dental Medicine who graduated during the period 2002-04. Associations between predictors and outcomes were first evaluated individually. Any associations that were near statistically significant (p=0.15) were then included in a multiple linear regression model. The criterion for statistical significance in the multiple linear regression model was p=0.05. While a number of measures were associated in bivariate analyses, few predictors were statistically significantly associated with clinical outcomes in the multiple regression analyses. Those predictors that were associated with clinical outcomes were also not consistently associated with the different outcomes studied. These data indicate that, within this study population, there is little to no uniform association between preclinical didactic performance and measurements of clinical productivity and clinical proficiency. It is possible that the overlap in skill sets required for success in the predental/preclinical and clinical areas is minimal.

Clinical Competence↗
PubMed1991

[Kindling effect in models of epilepsy induced by clinrats].

In order to create chemical kindling effect model of epilepsy, fifty-six adult male SD rats were used in this experiment, and randomly divided into five groups. An intramuscular injection of various subthreshold dose of CL (0.50, 0.75, 1.00, 1.25 mg/kg) was given repeatedly per 3.5 days in the I-IV groups, V group received injections of normal saline of the same volume as control. ECoG and EHG were recorded by telemetric method through electrodes chronically implanted in the cortex and hippocampus. The behavior of them was observed at the same time. The results of experiments showed that: 1. CL can lead to the typical behavior, ECoG and EHG of epilepsy. So it is an effective chemical kindling agent of causing epilepsy, and hippocampus was more than cortex to CL. 2. The relationship between the seizure stages induced by CL various dose groups and the mean injection times had a linear correlation through linear regressive processing (r value: 0.9276-0.99732). The difference comparison of linear regressive intercept of various groups was significant (P less than 0.05), respectively. It is indicated that the more the dose of CL increase, the less the injection times of reaching seizure stages. 3. 24 rats of the experimental groups 46 rats had reached kindling criterion through 40 times injection of CL. The difference comparison between I, II and III, IV groups of kindling rats was quite significant (P less than 0.01), respectively. 4. The mean persistence time of all kindled rats was 113.42 days. The longest persistence time of them was 224 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Structural changes in the peripheral nerves over a lifetime. Morphometric studies of the sciatic and sural nerves].

Investigations were conducted on topographically identical tissue samples from the sciatic and sural nerves. 22 autopsies on individuals free of any severe disorder provided the material for this study (stillborn babies and deaths of unnatural causes). The material was selected with the view to having all age groups of human life represented. preferably two or more subjects of each decade. The overall cross-section and the cross-section of each bundle were planimetrically measured, using magnified photographs of celloidin sections, 30 micron in thickness. Depending on age, the sum of the cross-sections of all bundles was found to percentually decrease by about one fifth in all nerves relative to the overall cross-section. Alterations in the sural nerve and in the smaller portion of the sciatic nerve (N. peronaeus communis) were characterised by linear regression of measurements with a negative correlation, but non-linear regression could be estimated for the larger portion (N. tibialis). Semi-thin sections of methacrylate-embedded material were used to ascertain the numerical density of Schwann cell nuclei on all cases and to study fibre calibre distribution on three selected subjects. The averaged numerical density of Schwann cell nuclei decreased by about 80% from birth to the age of five years and varied between the second and fifth decades within a relatively small range described by a hyperbolic regression. No unambiguous correlation was found to exist beyond the fifth decade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1981

Long-term stability of a stabilized liquid quality-control serum.

To evaluate the long-term stability of a new liquid quality-control serum ("Decision", Beckman Instruments, Inc.) stabilized with ethylene glycol (330 mL/L), we analyzed it for 22 commonly measured analytes during storage at 2--8 degrees C for 24 days or -15 to -20 degrees C for 55 weeks. Three separate laboratories replicated the analyses, using various analytical methodologies. The data were subjected to linear regression analysis, regressing concentration on time. Analytes were considered unstable when the linear regression coefficient was unequal to zero with 95% or greater probability in all three laboratories. By this criterion all of the analytes were stable for at least 24 days when the control serum was stored at refrigerator temperature and for at least 55 weeks at freezer temperature. We conclude this material is a satisfactory substitute for existing lyophilized quality-control materials and offers certain advantages: stability, vial-to-vial uniformity, decreased waste, and eliminated reconstitution.

Blood Chemical Analysis↗
PubMed1994

Multilevel models for hierarchically nested data: potential applications in substance abuse prevention research.

This chapter reports on an application of a multilevel analysis. A multilevel analysis is a data analysis that uses variables that are measured at different levels of the hierarchy. A hierarchy can have many levels, such as student level, class level, school level, and State or country level, where students are nested within classes, classes are nested within schools or school districts, and school districts can be nested within towns, States, or countries. As soon as one pays attention, hierarchies are present in all data. In large-scale prevention research, researchers usually have information about two or more levels involved, for instance, variables describing individuals (such as achievement, drug use, gender, and measures of socioeconomic status or home environment); variables describing schools (such as school environment, urban versus rural, and type of treatment administered); and perhaps variables describing districts, States, or countries. It is well known that the analysis of variables (i.e., measures at different levels of the hierarchy) on any of these levels separately can be misleading, as will be shown in this chapter. It is more satisfactory to construct a model and technique that simultaneously take information on all levels into account. This chapter introduces such a multilevel model for hierarchically nested data by evaluating the effect of a drug prevention program, Normative Education (NORM), wherein data are collected on students nested within schools. The model is a linear regression model. The difference between this model and the traditional linear regression model is that it takes the intraclass correlation into account and treats variables measured at different levels of the hierarchy in a more appropriate way.

Analysis of Variance↗
PubMed2002

EMG and oxygen uptake responses during slow and fast ramp exercise in humans.

This study examined the relationship between muscle recruitment patterns using surface electromyography (EMG) and the excess O(2) uptake (Ex.V(O(2))) that accompanies slow (SR, 8 W min(-1)) but not fast (FR, 64 W min(-1)) ramp increases in work rate (WR) during exercise on a cycle ergometer. Nine subjects (2 females) participated in this study (25 +/- 2 years, +/- S.E.M.). EMG was obtained from the vastus lateralis and medialis and analysed in the time (root mean square, RMS) and frequency (median power frequency, MDPF) domain. Results for each muscle were averaged to provide an overall response and expressed relative to a maximal voluntary contraction (%MVC). Delta.V(O(2))/DeltaWR was calculated for exercise below (S(1)) and above (S(2)) the lactate threshold (LT) using linear regression. The increase in RMS relative to the increase in WR for exercise below the LT (DeltaRMS/DeltaWR-S(1)) was determined using linear regression. Due to non-linearities in RMS above the LT, DeltaRMS/DeltaWR-S(2) is reported as the difference in RMS (DeltaRMS) and the difference in WR (DeltaWR) at end-exercise and the LT. SR was associated with a higher (P < 0.05) Delta.V(O(2))/DeltaWR (S(1), 9.3 +/- 0.3 ml min(-1) W(-1); S(2), 12.5 +/- 0.6 ml min(-1) W(-1)) than FR (S(1), 8.5 +/- 0.4 ml min(-1) W(-1); S(2), 7.9 +/- 0.4 ml min(-1) W(-1)) but a similar DeltaRMS/DeltaWR-S(1) (SR, 0.11 +/- 0.01% W(-1); FR, 0.10 +/- 0.01 % W(-1)). Ex.V(O(2)) was greater (P < 0.05) in SR (3.6 +/- 0.7 l) than FR (-0.7 +/- 0.4 l) but was not associated with a difference in either DeltaRMS/DeltaWR-S(2) (SR, 0.14 +/- 0.01% W(-1); FR, 15 +/- 0.02 % W(-1)) or MDPF (SR, 2.6 +/- 5.9 %; FR, -15.4 +/- 4.5 %). The close matching between power output and RMS during SR and FR suggests that the Ex.V(O(2)) of heavy exercise is not associated with the recruitment of additional motor units since Ex.V(O(2)) was observed during SR only. Compared to the progressive decrease in MDPF observed during FR, the MDPF remained relatively constant during SR suggesting that either (i) there was no appreciable recruitment of the less efficient type II muscle fibres, at least in addition to those recruited initially at the onset of exercise, or (ii) the decrease in MDPF associated with fatigue was offset by the addition of a higher frequency of type II fibres recruited to replace the fatigued motor units.

Adult↗
PubMed2002

Evaluation of a novel structural model to describe the endogenous release of lead from bone.

The aim of this paper was to assess the endogenous release of lead from bone to blood, in 204 exposed subjects. resuming their duties after a 10-month strike in a primary lead smelter in 1991. In vivo 109Cd K X-ray Fluorescence (109Cd K XRF) was used to measure the bone lead concentration in tibia and calcaneus in the smelter, in 1994 and five years later. The 1994 data were used to derive the post-strike bone lead concentrations retrospectively from the significant association between bone lead and the cumulative blood lead index (CBLI). When a linear model was used to predict the current blood lead upon the level of lead in bone, structural analysis of the data produced slopes for tibia (2.0, 95% CI 1.66-2.54) and calcaneus (0.19, 95% CI 0.16-0.23) that were significantly higher than those predicted by the commonly used simple linear regression method, for tibia (0.73, 95%, CI 0.58-0.88) and calcaneus (0.08, 95% CI 0.06-0.09). This suggests that more lead than previously predicted by regression is released from bone to blood. Furthermore, the structural analysis of the data produced an estimation of the contribution of the bone lead stores to the bloodstream that was more consistent with the 1999 epidemiological data than did the regression estimation. Moreover, a non-linear relationship between tibia lead and blood lead was suggested from the assumption checking procedures for regression. When a non-linear regression model was fit to the data, the method produced estimates of important parameters in human lead kinetics, namely the blood lead saturation constant, showing a good agreement with current knowledge of lead metabolism. Finally, the likelihood of a non-linear bone lead release seems to be supported by the recently described dependence of the half-life of lead in bone on age and intensity of occupational exposure.

Adult↗