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PubMed2000

Close relationship of abnormal glucose tolerance with endothelial dysfunction in hypertension.

Hypertension is frequently accompanied by left ventricular hypertrophy, endothelial dysfunction, and abnormal glucose metabolism. However, no study has examined the relative pathological significance of left ventricular hypertrophy and abnormal glucose metabolism on endothelial dysfunction in hypertension. This study was conducted to evaluate whether abnormal glucose tolerance assessed by 75-g oral glucose tolerance test or left ventricular hypertrophy is more closely associated with endothelial dysfunction in never-treated hypertensive patients without elevated fasting blood glucose. We studied 107 unmedicated hypertensive patients (mean age, 54+/-10 years) whose fasting blood glucose was <7.0 mmol/L. Endothelial function was assessed by change in brachial artery diameter in response to reactive hyperemia, and left ventricular mass index was determined by ultrasonography. Simple linear regression analysis demonstrated that endothelial function significantly correlated with left ventricular mass index and 2-hour blood glucose in 75-g oral glucose tolerance test, but not with fasting blood glucose. Multiple linear regression analysis revealed that endothelial function significantly correlated with 2-hour blood glucose (beta=-2.68, P<0.05) after we controlled for other clinical variables. Patients were divided into 3 groups according to 2-hour blood glucose levels. Endothelial function was more impaired in patients with diabetes (n=12; 4.7+/-1.8%) and in those with impaired glucose tolerance (n=31; 6.3+/-2.9%) than in those with normal glucose tolerance (n=64; 8.4+/-4.5%) (P<0.05), but left ventricular mass index was similar in these 3 groups. Abnormal glucose tolerance assessed by 75-g oral glucose tolerance test, rather than left ventricular hypertrophy, may have direct pathophysiological relevance to endothelial dysfunction in borderline to moderate hypertensive patients.

Adult↗
PubMedDate not supplied

[Prediction of binding affinities of protein-ligand complexes using nonlinear models].

A network model for prediction of the free energy changes in protein-ligand complexes has been developed. The 150 complexes of different nature were used as a training set. The computational physics-chemical parameters of these complexes were used as independent variables. Both classical models of multiple linear regression and several network models with one hidden layer were created and the best was chosen. Significant improvement was shown for network model prediction quality in comparison with classical model of multiple linear regression (R2 on training--0.81 and 0.54; R2 on "leave-one-out" procedure--0.74 and 0.52 respectively).

Ligands↗
PubMedDate not supplied

Homocysteine level and coronary artery disease.

Atherosclerosis, and its most common manifestation, coronary artery disease (CAD), are rather common causes of morbidity and mortality worldwide. Recognition of its various risk factors is important to planning effective preventive measures. After the homocysteine theory was presented in 1969, attention has been directed toward the serum homocysteine level as a coronary artery disease risk factor. The authors aimed to assess the relationship between hyperhomocysteinemia and CAD in an Iranian population. In a case control study, 197 individuals (male: 123 [62.4%]) who were scheduled for coronary angiography were selected. Venous samples were taken from the patients in fasting state before angiography. Data about age, sex, risk factors (eg, hypertension, diabetes, smoking, hyperlipidemia, obesity) were obtained from prepared questionnaires. Homocysteine levels in patients were measured by ELISA method. A homocysteine level above 15 mumol/liter was considered high. Angiography reports and homocysteine levels were analyzed by independent sample t test, one-way ANOVA, multiple linear regression, and stratified analysis. In comparison with the patients with normal angiography reports (32.5%), patients with abnormal angiography reports (67.5%) had increased levels of homocysteine (p = 0.001). About 28.1% of patients with normal angiography reports had hyperhomocysteinemia. After further evaluation, linear correlations were detected between the numbers of involved vessels and homocysteine level (p = 0.000). Multiple linear regression analysis of data detected that in individuals without any risk factors, the relationship was stronger and more meaningful (p = 0.000). These data show that hyperhomocysteinemia is related to CAD as an independent risk factor. In individuals without any risk factors a linear correlation between homocysteine level and numbers of coronary artery involvement was present. If this equation is confirmed prospectively in other studies, the level of plasma homocysteine may he used as a noninvasive way of predicting the number of diseased coronary arteries.

Adult↗
PubMed1996

Lymphocyte beta2-adrenergic receptors and plasma catecholamine levels in lead-exposed workers.

The effect of lead exposure on beta2-adrenoceptor density and catecholamine response was studied in 26 male workers and 1 female worker, exposed to lead on average for 6 years. The systolic blood pressure in lead workers (101-160 mmHg, 124.4 +/- 14.7 mmHg) was found to be significantly higher than in controls (97-134 mmHg, 115.4 +/- 10.4 mmHg, p < 0.01) as was plasma norepinephrine (0.51 +/- 0.1 microg/liter vs 0.24 +/- 0.05 microg/liter, p < 0.01). The density of lymphocyte beta2-adrenergic receptors (Bmax) in lead-exposed workers was 86% lower than that in controls (0.15 +/- 0.08 vs 1.08 +/- 0.29 fmol/0.1 x 10(6) cells; p < 0.01). The dissociation constants (Kd) of [125I]iodocyanopindolol were 93.6 +/- 42.6 and 87.9 +/- 42.7 pM in lead-exposed workers and controls, respectively. Multiple linear regression analysis showed that elevation of systolic pressure was closely related to (a) blood lead levels, (b) decreased beta2-adrenergic receptor density, and (c) increased plasma catecholamine levels in lead-exposed workers. Linear regression analysis revealed that both plasma norepinephrine levels and beta2-adrenoceptor density (Bmax) were highly correlated with both systolic blood pressures and blood lead levels in lead-exposed workers, and a highly significant negative correlation was found to exist between Bmax and plasma norepinephrine levels (r = -0.82, p < 0.001). These data therefore demonstrate that there is a close relationship between elevated plasma catecholamine levels, decreased beta2-adrenergic receptors, and elevated blood pressure in lead-exposed workers.

Adult↗
PubMed2006

Health-related quality of life among self-reported arthritis sufferers: effects of race/ethnicity and residence.

OBJECTIVE: We evaluated differences in health-related quality of life (HRQoL) for African Americans and Caucasians with self-reported arthritis residing in rural and urban areas of a southern state. METHODS: 1,191 individuals completed a telephone survey, which included the 12-Item Short Form Health Survey (SF-12). Participants were stratified into groups: African American/rural, Caucasian/rural, African American/urban, and Caucasian/urban. We evaluated differences and associations in HRQoL for the four groups. RESULTS: Multivariable linear regression models revealed that being an African American rural resident was associated with worse self-reported mental health on the SF-12 even after adjusting for multiple confounding variables. In contrast, multivariable linear regression models revealed that being a Caucasian rural resident was associated with worse physical health SF-12 scores. CONCLUSIONS: The study revealed differences in HRQoL on the mental and physical health functioning scales of the SF-12 for African American rural and Caucasian rural residents. Researchers assessing HRQoL in arthritis patients should consider using a race/residence product term in their analyses.

Black or African American↗
PubMed1987

Protein requirements of subadult nilgai antelope.

1. The maintenance crude protein (CP) requirements of subadult nilgai antelope (Boselaphus tragocamelus) were determined by nitrogen balance. Four isocaloric pelleted diets, ranging from 8.4 to 23.8% CP, were fed. 2. Subadults maintained a positive nitrogen balance on all diets. Linear regression showed that 95.8% of diet CP was truly digested and estimated metabolic fecal nitrogen (NFN) excretion at 0.388 gN/W0.75/day. 3. Estimates for endogenous urinary nitrogen excretion and maintenance nitrogen requirement, derived through linear regression, were erroneous. Consequently, the former was calculated based on metabolic size (0.126 gN/W0.75/day) and added to MFN to obtain an 0.514 gN/W0.75/day estimate of required nitrogen for maintenance. This value is between the levels recommended for maintenance of yearling deer and cattle. 4. Given the same level of dry matter intake (68.6 g/W0.75/day) and true CP digestibility, study animals would be able to meet N equilibrium on a 4.89% CP (dry matter basis) diet. 5. Based on data from other sources, natural diets containing 6.98% CP would need to be consumed by free-ranging subadults to maintain body weight.

Aging↗
PubMed1991

Biotin diffusion in stored chicken eggs: a re-assessment.

1. The possibility that biotin in stored eggs migrates from the yolk into the albumen was re-investigated. 2. Sets of eggs collected from 12 Single Comb White Leghorn hens were stored at 5, 8, 12, 15, or 18 degrees C for 5, 10, 15, 20, or 25 days and then frozen. 3. For each set, yolk and albumen samples adjacent to the yolk membrane were each pooled and assayed for protein-bound biotin by radioligand exchange with non-linear regression analysis of the data. 4. In contrast to previous work reported by Bush and White (Comp. Biochem. Physiol. 93B, 543-547, 1989), no evidence of biotin diffusion was found. 5. Non-linear regression was used to re-evaluate the data from the earlier study, confirming the results, although less strikingly. 6. The discrepancy is partly due to the method of data analysis, although differences in breed or number of hens may also be contributing factors.

Animals↗
PubMed1988

Progressive ratio performance maintained by buprenorphine, heroin and methadone in Macaque monkeys.

The relative reinforcing efficacy of buprenorphine (0.01-0.10 mg/kg/inj.), heroin (0.01-0.10 mg/kg/inj.), methadone (0.03-0.25 mg/kg/inj.) and saline were compared in Macaque male monkeys using progressive ratio procedures. Responding for drugs and food (1 g banana pellet) was maintained on a second order FR 4 (VR 16:S) schedule of reinforcement that required an average of 64 responses for each injection or food pellet. After 40 sessions (10 days) of stable performance, the number of responses for each drug injection was systematically increased until monkeys reached a breakpoint defined by 2 consecutive days of no drug injections. Progressive ratio breakpoints for heroin at intermediate and high doses (0.05 and 0.10 mg/kg/inj.) were two to three times higher than for any other drug (P less than 0.05). Breakpoints for buprenophine (0.01-0.10 mg/kg/inj.) were higher than for a low dose of methadone (0.03 mg/kg/inj.) but were equivalent to an intermediate methadone dose (0.10 mg/kg/inj.). Breakpoints for both low (0.01 mg/kg/inj.) and high (0.10 mg/kg/inj.) buprenorphine doses were greater than for intermediate doses (0.03 and 0.05 mg/kg/inj.) but these differences were not statistically significant. Linear regression and area under the curve analyses were used to quantify the rate at which drug maintained responding decreased by 30% of control levels as response requirements were increased. Extrapolated breakpoints derived from linear regression analyses were significantly correlated (P less than 0.05-0.01) with actual breakpoints for buprenorphine, heroin and methadone. The concordance between 'extrapolated' and traditional breakpoint ranking of these drugs suggests that regression analysis techniques can be used to predict traditional breakpoints.

Animals↗
PubMed2005

Effects of morphine and its metabolites on immune function in advanced cancer patients.

STUDY OBJECTIVE: To determine whether morphine and its active metabolites such as morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G) modulate immune function in patients with advanced cancer who required morphine for pain relief. DESIGN: Prospective observational clinical study. SETTING: Pain clinic of a university hospital. PATIENTS: Fifteen patients who visited our clinic for control of advanced cancer pain. INTERVENTIONS: During the initiation or changes of morphine therapy, venous blood samples were obtained at the enrollment of this study, 1 and 3 weeks after the change of morphine dose or route. MEASUREMENTS: Lymphocyte subpopulation CD4+ and CD8+, activity of natural killer cell, phytohemagglutinin (PHA)-induced T-cell proliferation, and plasma immunoglobulin M and G concentrations were measured, as well as plasma concentrations of morphine, M-3-G, and M-6-G. MAIN RESULTS: At the entry of the study, 6 patients did not receive any type of morphine medication (group 1), whereas 9 patients were treated with morphine for 1 month (group 2). Cancer pain, rated as 4 at the entry period, was reduced to 2 of 10 (visual analogue scale) during the study periods. Although the plasma concentrations of M-3-G and M-6-G in Group 1 were significantly less than those in Group 2, plasma concentrations of immunologic markers were similar between the groups. In Group 1, Spearman linear regression analysis showed negative correlation between morphine-derived metabolites and immunoglobulins or PHA-induced T-cell proliferation, whereas poor correlation was found with all immunologic parameters in Group 2. Stepwise linear regression analyses showed that the metabolites, rather than morphine per se, modulated immune function, reflected by PHA-induced T-cell proliferation and immunoglobulin G concentration in Group 1. CONCLUSIONS: The present study suggests that some of humoral and cellular immunity are modulated by morphine-derived metabolites at the early phase of morphine therapy in patients with advanced cancer.

Adult↗
PubMed2003

Pulmonary blood pressure, not flow, is associated with net endothelin-1 production in the lungs of patients with congenital heart disease and normal pulmonary vascular resistance.

OBJECTIVE: Endothelin-1 concentrations are increased in patients with increased mean pulmonary arterial pressure, pulmonary blood flow, and pulmonary vascular resistance. However, endothelin-1 concentrations have not been well characterized in patients with congenital heart disease and normal pulmonary vascular resistance. In particular, it is unclear whether pressure or flow is the key regulator of endothelin- 1 in this setting. We tested the hypothesis that pulmonary blood pressure and not flow is associated with net endothelin-1 production in patients with congenital heart disease and normal pulmonary vascular resistance. METHODS: With a commercially available immunoassay, we measured endothelin-1 concentrations in pulmonary arterial and pulmonary venous plasma of 56 consecutive patients with congenital heart disease and pulmonary vascular resistance less than 2 U. m(2) undergoing cardiac catheterization. We used multiple linear regression to analyze the effect of demographic and hemodynamic variables on pulmonary arterial and venous endothelin-1 concentrations and on the change of endothelin-1 concentration over the pulmonary vascular bed. RESULTS: Multiple linear regression revealed that of all the hemodynamic variables tested, mean pulmonary arterial pressure had the greatest effect on increasing the change of endothelin-1 concentration over the pulmonary vascular bed (P <.0001). Pulmonary blood flow did not have any effect on endothelin-1 concentrations or on the change of endothelin-1 concentration over the pulmonary vascular bed. CONCLUSIONS: This study shows that pulmonary blood pressure and not flow is associated with net endothelin-1 production in patients with congenital heart disease and normal pulmonary vascular resistance.

Blood Pressure↗
PubMed2003

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PURPOSE: To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. DESIGN: Retrospective observational case series. PARTICIPANTS: Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. METHODS: Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. MAIN OUTCOME MEASURES: The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). RESULTS: The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). CONCLUSIONS: Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Adult↗
PubMed2001

Inter fraction variations in rectum and bladder volumes and dose distributions during high dose rate brachytherapy treatment of the uterine cervix investigated by repetitive CT-examinations.

PURPOSE: To evaluate variation of dose to organs at risk for patients receiving fractionated high dose rate gynaecological brachytherapy by using CT-based 3D treatment planning and dose-volume histograms (DVH). MATERIALS AND METHODS: Fourteen patients with cancer of the uterine cervix underwent three to six CT examinations (mean 4.9) during their course of high-dose-rate brachytherapy using radiographically compatible applicators. The rectal and bladder walls were delineated and DVHs were calculated. RESULTS: Inter fraction variation of the bladder volume (CV(mean)=44.1%) was significantly larger than the inter fraction variation of the mean dose (CV(mean)=19.9%, P=0.005) and the maximum dose (CV(mean)=17.5%, P=0.003) of the bladder wall. The same trend was seen for rectum, although the figures were not significantly different. Performing CT examinations at four of seven brachytherapy fractions reduced the uncertainty to 4 and 7% for the bladder and rectal doses, respectively. A linear regression analysis showed a significant, negative relationship between time after treatment start and the whole bladder volume (P=0.018), whereas no correlation was found for the rectum. For both rectum and bladder a linear regression analysis revealed a significant, negative relationship between the whole volume and median dose (P<0.05). CONCLUSION: Preferably a CT examination should be provided at every fraction. However, this is logistically unfeasible in most institutions. To obtain reliable DVHs the patients will in the future undergo 3-4 CT examinations during the course of brachytherapy at our institution. Since this study showed an association between large bladder volumes and dose reductions, the patients will be treated with a standardized bladder volume.

Adult↗
PubMed1998

Strychnine-insensitive [3H] glycine binding to synaptosomal membranes from the chick retina.

The pharmacology and kinetics of strychnine-insensitive [3H] glycine binding to synaptic membranes from the outer (P1) and the inner (P2) plexiform layers of chick retina was studied. Inhibition curves for glycine, D-serine, 1-amincyclopropanecarboxylic acid (ACPC) and strychnine were analyzed by non-linear regression. Hill slopes for glycine and D-serine were not different from unity, whereas those for ACPC were < 1 in both fractions, revealing heterogeneity of binding sites in these membranes. Non-linear regression analysis of time course and saturation experiments strengthen the idea that [3H] glycine binds to more than one class of sites, with similar affinities at equilibrium. Antagonists of strychnine-insensitive glycine receptors in the CNS did not inhibit [3H] glycine binding to these membranes, which demonstrates that NMDA receptors in the retina have different structural requirements for ligand interaction at these sites. pH affected the specific binding, in agreement with the participation of specific amino acid residues at glycine binding sites on NMDA receptors, and also with functional studies in which the modulation of affinity at this site by protons has been observed. These results support previous studies regarding CPP and MK-801 binding, and provide evidence which indicates that the pharmacophore for glycine and other NMDA-related ligands is distinct for the retina, compared to the CNS, mainly regarding the effects of glycine-site antagonists.

Animals↗
PubMed2005

Improving the repeatability of Heidelberg retina tomograph and Heidelberg retina tomograph II rim area measurements.

AIMS: To devise and test strategies for improving Heidelberg retina tomograph (HRT and HRT-II) rim area (RA) repeatability and assess the benefit of the strategies in time series of HRT images. METHODS: The effect of the standard and 320 microm reference planes and image quality on RA repeatability was assessed in a test-retest HRT image dataset from 74 subjects. A longitudinal HRT image dataset from 30 ocular hypertensive subjects was analysed by linear regression of RA over time, with each of the reference planes and using a manual image alignment facility. RA variability was estimated by comparing the standard deviation of residuals (RSD) generated by each linear regression. RESULTS: RA repeatability was better with the 320 microm reference plane (repeatability coefficient 0.17 mm(2)), improving further with only good quality images (repeatability coefficient 0.08 mm(2)). For the longitudinal data, a significant (p<0.0001) reduction in the RSD from 0.10 to 0.05 mm(2) was obtained with the 320 microm reference plane. Manual alignment led to a further significant (p<0.0001) reduction in the RSD to 0.04 mm(2). CONCLUSIONS: The findings support the use of a 320 microm reference plane and manual image alignment to analyse RA over time. The estimates of RA repeatability may be used to define thresholds for glaucomatous change.

Adult↗
PubMed1993

The effect of maternal hypoxemia on the umbilical and femoral artery blood flow velocity waveforms and the relationship with mean arterial pressure in fetal sheep.

The relationship between the ratio femoral pulsatility index (PI)/umbilical PI and arterial oxygen content was examined in 8 fetal sheep at various stages of hypoxemia. This relationship was characterized by an inconsistent increase of the ratio femoral PI/umbilical PI at oxygen content levels beneath 1.0 mM. The correlation coefficient of the linear regression between both variables was only -0.54, indicating that prediction of fetal oxygenation on the basis of Doppler waveform measurements in peripheral fetal arteries might be invalid. The average correlation coefficient of the linear regressions between the femoral PI and fetal mean arterial pressure was 0.87 +/- 0.15 (SD), whereas the average correlation between the umbilical PI and fetal mean arterial pressure was 0.04 +/- 0.61. These data suggest that the degree of change in fetal mean arterial pressure considerably depends on the degree of change in vascular resistance in the fetal carcass.

Animals↗
PubMed1999

An analysis of the costs of ischemic stroke in an Italian stroke unit.

OBJECTIVE: To determine the direct costs of hospital care of acute ischemic stroke in a large Italian hospital, and to identify the main components of such costs. BACKGROUND: Cost containment in stroke care requires an up-to-date assessment of expenditures in the different areas of stroke management. However, costs may vary among countries because of different health system organizations. METHODS: All patients with ischemic stroke admitted during 1996 were considered. Total cost was the sum of a daily component, reflecting personnel wages and general care, and an ancillary component, reflecting mostly investigations and treatments. The real costs were used, not fixed charges. RESULTS: We included 245 patients, with a mean length of stay (LOS) of 13.1+/-7.0 days, and an in-hospital case fatality rate of 8.2%. The mean total cost per patient was 5,087,000+/-2,536,000 Italian Lira (LIT; $3,289+/-$1,640), with a mean cost per day of 388,000 LIT ($251). Approximately 80% of total costs were due to the daily component and 20% to the ancillary component. A multiple linear regression model of length of stay, which determines the daily cost, showed that the Rankin score at entry, the clinical syndrome type, and the destination at discharge independently contributed to LOS. A second linear regression model showed that younger age and longer LOS significantly increased ancillary costs. CONCLUSIONS: The containment of hospital costs of ischemic stroke may be achieved mostly through measures that reduce LOS, such as effective treatments and a quicker deployment.

Adult↗
PubMed2005

Detection of renal function decline in patients with diabetes and normal or elevated GFR by serial measurements of serum cystatin C concentration: results of a 4-year follow-up study.

Research on early renal function decline in diabetes is hampered by lack of simple tools for detecting trends (particularly systematic decreases) in renal function over time when GFR is normal or elevated. This study sought to assess how well serum cystatin C meets that need. Thirty participants with type 2 diabetes in the Diabetic Renal Disease Study met these three eligibility criteria: GFR >20 ml/min per 1.73 m2 at baseline (based on cold iothalamate clearance), 4 yr of follow-up, and yearly measurements of iothalamate clearance and serum cystatin C. With the use of linear regression, each individual's trend in renal function over time, expressed as annual percentage change in iothalamate clearance, was determined. Serum cystatin C in mg/L was transformed to its reciprocal (100/cystatin C), and linear regression was used to determine each individual's trend over time, expressed as annual percentage change. In paired comparisons of 100/cystatin C with iothalamate clearance at each examination, the two measures were numerically similar. More important, the trends in 100/cystatin C and iothalamate clearance were strongly correlated (Spearman r = 0.77). All 20 participants with negative trends in iothalamate clearance (declining renal function) also had negative trends for 100/cystatin C. Results were discordant for only three participants. In contrast, the trends for three commonly used creatinine-based estimates of GFR compared poorly with trends in iothalamate clearance (Spearman r < 0.35). Serial measures of serum cystatin C accurately detect trends in renal function in patients with normal or elevated GFR and provide means for studying early renal function decline in diabetes.

Adult↗
PubMed1992

Interconvertibility of asbestos fibre count concentrations recorded by three most frequent methods.

Simultaneous airborne chrysotile asbestos fibre samples were collected with three types of instruments, namely, the konimeter, the thermal precipitator and the membrane filter, in four asbestos plants (textile manufacturing, asbestos cement production, mining, milling). Linear regression analyses were performed of the membrane filter on the konimeter and thermal precipitator count concentrations, respectively. Sampling was performed at 24-35 locations in each of the processes studied. In order to linearize the relationships and to stabilize the sample variances the data were transformed using the transformation ln(x+1) for both the predictor and the response variables. Eight linear regression equations were developed. The slope coefficients of regressions differed significantly (P < 0.05 or < 0.01) between all the asbestos processes except for the differences of coefficients in mining and milling (P > 0.05). It is concluded that no single conversion factor can be used to reliably convert the konimeter or thermal precipitator to membrane filter asbestos fibre concentrations; a separate conversion factor must be derived for each technological process. In this case the confidence limits of estimates are acceptable for practical occupational hygiene purposes.

Air Pollutants, Occupational↗