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Results for “multiple linear regression”

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PubMed1996

The inhibition of alpha-chymotrypsin predicted using theoretically derived molecular properties.

The structures and molecular properties of 95 aromatic and heteroaromatic ligands previously tested as reversible inhibitors of chymotrypsin catalysis have been calculated using AMl. The properties obtained have been used as input for multiple linear regression analysis and as descriptors for a back-propagation neural network to predict the binding affinity of alpha-chymotrypsin inhibitors. Using polarizability, molecular shape, electrostatic similarity, dipole moment, ClogP, and the diagonalized quadrupole moments of the ligands, correlation coefficients between calculated and experimental affinities of 0.96 for the training set and 0.89 for the test set were obtained using a neural network. The performance of the multiple linear regression was significantly worse, although useful QSARs were also obtained.

Binding Sites↗

PubMedDate not supplied

A comparison of caries rates in non-institutionalized individuals with and without Down syndrome.

The caries rate of people with Down syndrome (DS) was compared to an age-matched control population without DS. A cross-sectional study design was used. Caries rates were assessed by an adjusted DFT score, expressed as a proportion of number of teeth in the mouth, to control for hypodontia in the subjects with DS. Bivariate and multiple linear regression analyses were used to compare caries rates in persons with and without DS. The sample size was 128, in which 44 were subjects with DS and 84 were subjects without DS. On a range of 0-1, the mean adjusted DFT scores were 0.10 in subjects with DS and 0.18 in the control group. Although this difference was significant at the bivariate level of analysis, in the multiple linear regression model, adjusted DFT was associated with age and professional fluoride therapy only. When expressed as a proportion of number of teeth, caries rates were not different in people with and without DS.

Adolescent↗

PubMed2005

Brain white matter hyperintensities: relative importance of vascular risk factors in nondemented elderly people.

PURPOSE: To prospectively determine whether there is an association between brain white matter signal hyperintensities on magnetic resonance (MR) images and potential risk factors for cerebral ischemia in a well-characterized narrow age cohort of nondemented community-dwelling elderly people. MATERIALS AND METHODS: The study population consisted of surviving members of the Aberdeen 1921 Birth Cohort, a subsample of participants in the 1932 Scottish Mental Survey who were born in 1921. With the permission of the local ethics committee and with informed written consent, 106 nondemented subjects (62 men, 44 women) aged 78-79 years underwent T2-weighted brain MR imaging. Brain MR images were scored semiquantitatively for deep white matter hyperintensities and periventricular hyperintensities. Vascular risk factors and clinical measures potentially associated with cerebral ischemia included hypertension, diabetes, cerebrovascular disease, smoking, body mass index grade, respiratory function levels (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], and peak expiratory flow rate [PEFR]) normalized for subject's height, plasma lipid levels (cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein), glycated hemoglobin level, and mean fasting blood glucose level. Pearson correlation coefficients were calculated for correlations between potential vascular risk factors and scores for deep white matter and periventricular hyperintensities, and stepwise multiple linear regression analysis was performed for factors with a statistically significant correlation. RESULTS: Significant Pearson correlations with deep white matter hyperintensities were found for glycated hemoglobin level (r = 0.31), hypertension (r = 0.27), normalized FEV1 (r = -0.27), normalized FVC (r = -0.22), normalized PEFR (r = -0.27), low-density lipoprotein (r = 0.24), and cholesterol (r = 0.20), and with periventricular hyperintensities for glycated hemoglobin level (r = 0.28) and normalized PEFR (r = -0.23). Multiple linear regression analysis showed that glycated hemoglobin level and hypertension were predictive of 16.2% of the variance in deep white matter hyperintensities. When subjects with non-insulin-dependent (type 2) diabetes mellitus (n = 11) were excluded, hypertension and decreased normalized PEFR were predictive of 11.7% of the variance. CONCLUSION: White matter hyperintensities are associated with elevated levels of glycated hemoglobin in nondemented community-dwelling elderly subjects. Hypertension and decreased normalized PEFR are the principal predictors of deep white matter hyperintensities in nondiabetic subjects.

Aged↗

PubMed2002

[Total plasma homocysteine levels. Relationship with plasmatic folic acid levels and 677C T polymorphism of 5,10-methylenetetrahydrofolate reductase].

BACKGROUND: Moderately increased plasma homocysteine (Hcy) in children has been associated with stroke and venous thrombosis and with a parental history of cardiovascular disease (CVD). Evaluation of Hcy concentrations during childhood and study of the factors determining its concentrations could play an important role in the primary prevention of CVD. Objective To detect cases of hyperhomocystinemia and to examine the association between Hcy levels and plasma folic acid levels and 677C T polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR). METHODS: The relationship between plasma Hcy levels, plasma folic acid levels, and the three genotypes of 677C T MTHFR polymorphism was investigated in 127 children (aged 2-18 years) and in 105 parents by multiple linear regression. RESULTS: The median Hcy levels were 5.00 mol/l in the children and 8.00 mol/l in the parents. Plasma folic acid levels were normal in all of the patients. The prevalence of the three genotypes in the children was 32.3 % for the CC genotype, 42.5 % for the CT genotype and 15.7 % for the TT genotype. Hcy concentrations were significantly higher in children with the TT genotype (p 0.018). Multiple linear regression revealed a positive direct effect of age (b 0.029, p 0.002) and a negative effect of genotype TT (b 3.886, p 0.002) on Hcy concentration. Hcy concentration was inversely correlated with folic acid levels but this correlation did not reach statistical significance. CONCLUSIONS: No cases of hyperhomocystinemia were found. To evaluate Hcy, age and plasma folic acid levels have to be taken into account in case there is a 677C T mutation. Hcy concentrations should be determined in older children with a family history of atherothrombosis and other risk factors for premature CVD.

Adolescent↗

PubMedDate not supplied

Exposure levels and determinants of softwood dust exposures in BC lumber mills, 1981-1997.

Measurements of personal exposure to wood dust (n = 1237) collected by the Workers' Compensation Board of British Columbia, Canada, over the period 1981-1997 were used to construct an empirical model to identify broad determinants of softwood dust exposure. Potential determinants of exposure examined included species of tree processed; company; geographic location of lumber mill; department; job title; calendar year; and production factors such as board feet of lumber produced per year. A determinants of exposure model was built using multiple linear regression. Nested within this compliance database was a subset of samples collected for a research study. These enabled the authors to explore whether differences in exposure measurements can in part be explained by sampling strategy (research versus compliance). Potential differences were examined by examining differences in means for each job title, stratified by sampling strategy; and by offering "sampling strategy" as a categorical predictor variable to the empirical model. Multiple linear regressions revealed the most important determinants of increased wood dust exposure to be mill location away from the coast, earlier calendar year, and indoor jobs. The empirical model had an R2 of 0.39 and a predictive range from 0.02 to 25.45 mg/m3. Research and compliance sampling strategies showed no difference in mean exposure and distribution in the empirical model (p < 0.05), suggesting that regulatory exposure databases may be of utility for exposure assessment in epidemiology. This research indicates that compliance-sampling strategies do not result in an overestimation of mean exposure levels within jobs, but they do focus on a biased sample of jobs-those most highly exposed.

Air Pollutants, Occupational↗

PubMed2001

Results of respiratory mechanics analysis in the critically ill depend on the method employed.

OBJECTIVE: To compare the measurements of total resistance and dynamic elastance determined by different techniques of respiratory mechanics analysis based on the time or frequency domains. DESIGN: Prospective study. SETTING: A 12-bed medical and surgical intensive care unit in a 700-bed university hospital. PATIENTS: Eighteen sedoparalyzed patients who needed controlled mechanical ventilation for acute or chronic acute respiratory failure. MEASUREMENTS: The total resistance and dynamic elastance in the time domain were determined by the occlusion technique and by multiple linear regression. The Fourier analysis was used to study the impedance of the respiratory system for elastance and resistance values in the frequency domain. RESULTS: The ANOVA analysis of the elastance variable showed no statistical differences (Ef: 41.4+/-19.0 cmH(2)O/l, Emlr: 40.8+/-17.2 cmH(2)O/l Edyn,occ: 39.5+/-14.0 cmH(2)O/l; ns) and the correlation was very good (r=0.8-0.9). The total resistances were less with multiple linear regression (13.5+/-9.3 cmH(2)O/l per s, p<0.05) than Rmax (17.0+/-11.9 cmH(2)O/l per s) or Rf (17.6+/-10.2 cmH(2)O/l per s). There were no differences between Rmax and Rf (p=0.7) and the correlation between resistances was 0.7-0.9. The agreement analysis for variables without statistical differences showed the following limits: Edyn,occ-f: -17 to 13 cmH(2)O/l; Edyn,occ-mlr: -12 to 9 cmH(2)O/l; Emlr-f: -6 to 8 cmH(2)O/l; Rmax-f: -18 to 19 cmH(2)O/l per s. This last range was related to the autoPEEP level (r=0.9). CONCLUSION: The wide agreement limits show that respiratory mechanics analysis is very dependent on the measurement technique used, particularly for resistance, perhaps due to the higher dependence on frequency.

Acute Disease↗

PubMedDate not supplied

Glomerular filtration rate changes in normoalbuminuric and microalbuminuric Type 2 diabetic patients and normal individuals A 10-year follow-up.

AIM: To analyze the changes in the glomerular filtration rate (GFR) in a cohort of normoalbuminuric Type 2 diabetic (DM 2) patients and nondiabetic individuals. METHODS: Sixty-five normoalbuminuric DM 2 patients [urinary albumin excretion rate (UAER) <20 microg/min] and 44 nondiabetic individuals recruited at baseline were followed for a mean period of 10 +/- 1 years. In addition to conventional clinical and metabolic variables, GFR ((51)Cr-EDTA technique) and UAER (immunoturbidimetric method) measurements were performed at baseline and at follow-up. We also evaluated the presence of diabetic retinopathy, hypertension, and cardiovascular disease. Multiple linear regression was performed to assess variables independently associated with GFR evolution in patients with Type 2 diabetes. RESULTS: Fifty DM 2 patients and 32 nondiabetic individuals were included in the follow-up evaluation. Fourteen out of the 50 patients with Type 2 diabetes developed microalbuminuria. They presented a faster GFR decline (-0.39+/-0.24 ml/min/month; ANOVA, P=.0013) than did persistently normoalbuminuric (-0.16+/-0.16 ml/min/month) and nondiabetic individuals (-0.13+/-0.14 ml/min/month). Multiple linear regression analysis disclosed baseline fasting plasma glucose (FPG) along with the development of microalbuminuria as factors significantly related to a higher GFR decline. CONCLUSIONS: Persistently normoalbuminuric patients and normal individuals presented a similar degree of GFR reduction related to the aging process. The slope was significantly enhanced in patients who developed microalbuminuria and was influenced by worse baseline glucose control.

Albuminuria↗

PubMed2004

Ability of the actiwatch accelerometer to predict free-living energy expenditure in young children.

OBJECTIVE: To determine whether activity counts obtained with the Actiwatch monitor are associated with total expenditure and body composition in young children. RESEARCH METHODS AND PROCEDURES: Actiwatch activity monitors were tested in 29 children 4 to 6 years old under field conditions over eight days. Total energy expenditure (TEE) was assessed with the doubly labeled water (DLW) technique. Correlation analyses were used to identify variables related to energy expenditure and percentage body fat. Multiple linear regression analyses were used to examine the variance in TEE and percentage body fat explained by activity counts after adjusting for relevant covariates. RESULTS: Both average total daily activity counts (658,816 +/- 201,657) and the pattern of activity were highly variable among subjects. TEE was significantly related to lean body mass (r = 0.45) and age (r = 0.48; p < 0.05 for both). Activity counts alone were not associated with TEE. In multiple linear regression analyses, TEE was independently associated with only lean body mass. Percentage fat mass was independently associated with body weight, being a girl, and being white, but not with average total activity counts. DISCUSSION: Activity counts obtained with the Actiwatch under free-living conditions do not reflect TEE in 4- to 6-year-old children and are not correlated with percentage fat mass. Therefore, average total activity counts obtained with the Actiwatch may be of limited value in identifying children at risk for becoming obese.

Adipose Tissue↗

PubMed2003

Plasma adiponectin in overweight, nondiabetic individuals with or without insulin resistance.

AIM: Adiponectin is a protein produced exclusively by adipocytes with putative insulin-sensitizing and anti-atherogenic properties. This cross-sectional study investigated the relationship between plasma adiponectin and a range of anthropometric, glycaemic, lipid and inflammatory parameters in overweight and obese subjects expressing characteristics of the metabolic syndrome. METHODS: Subjects were selected for the study from a clinical database, if they were non-diabetic, overweight [body mass index (BMI) > 25] and had features of the metabolic syndrome. The subjects were grouped according to BMI (25-30, 31-35 and >35 kg/m2) and then stratified for insulin resistance [homeostasis model assessment (HOMA) %S]. One hundred and ninety-seven patients (109 males and 88 females) were selected for the study by taking an equal number with the highest and lowest HOMA indices from each of the three BMI groups. Plasma adiponectin concentration was measured in duplicate by radioimmunoassay, and the relationship between these levels and the other parameters was investigated using correlation and multiple linear regression analyses. RESULTS: Plasma adiponectin concentration was higher in females than males (median 10.3 vs. 7.1 micro g/ml, p < 0.001) despite being matched for BMI. In both genders, adiponectin levels were inversely related to BMI, waist circumference, percentage body fat, insulin resistance and the fasting plasma concentration of leptin. A direct correlation in both sexes was found between adiponectin levels and high-density lipoprotein (HDL)-cholesterol, apolipoprotein A1 and age. Multiple linear regression analyses showed that the independent determinants of low plasma adiponectin concentrations were gender, age, BMI, insulin resistance and HDL-cholesterol. An association between reduced adiponectin and increased high-sensitivity plasma C-reactive protein concentration was observed only in female subjects and was independent of anthropometric variables. Our observation that adiponectin levels increase with age differs from the majority of other studies and may simply reflect the demographics of the population studied. CONCLUSIONS: This study shows that adiponectin is an important molecular link between obesity, insulin resistance and atherogenic lipoproteins. It is possible that plasma adiponectin concentration may be a convenient marker for identifying subjects with the metabolic syndrome who may progress to impaired glucose tolerance. Longitudinal studies are required in order to verify this clinical application of adiponectin.

Adiponectin↗

PubMed1999

Weight-bearing physical activity, calcium intake, systemic glucocorticoids, chronic inflammation, and body constitution as determinants of lumbar and femoral bone mineral in juvenile chronic arthritis.

The associations between the lumbar and femoral bone mineral and several body constitutional, lifestyle, and disease related variables were studied in 111 children with juvenile chronic arthritis (JCA) by factor and multiple linear regression analyses. In addition to the measurement of bone mineral density (BMD), bone width and bone mineral volumetric density (BMDvol) were determined by dual-x-ray absorptiometry (DXA). Factor analysis of 13 explanatory variables yielded six non-correlating factors, named as body size, physical activity, calcium intake, glucocorticoids, disease duration, and disease activity. These six factors were used as new variables to explain BMD, BMDvol, and bone width by multiple linear regression analyses. These showed body size, physical activity, and calcium intake as significant positive and disease activity and glucocorticoids as significant negative determinants of BMD in JCA. The analyses revealed also considerable differences in the relationships between factors and BM Dvol or bone width.

Absorptiometry, Photon↗

PubMed1999

Helicobacter pylori infection and insulin requirement among children with type 1 diabetes mellitus.

OBJECTIVE: Helicobacter pylori induces gastric inflammation and the the production of cytokines in infected individuals. Theoretically, this increased production of cytokines could be deleterious for the control of the glycemia of patients with diabetes. This study aimed to describe the insulin requirement among patients with type 1 diabetes and H pylori infection compared with uninfected counterparts. METHODS: Cross-sectional design. Demographic information (age, gender, race, annual family income, and number of individuals per room in the household) and clinical information (age at diagnosis of diabetes, duration of illness, weight, height, compliance with clinical appointments, daily insulin units per kilogram of body weight [IU/kg/d], and glycosylated hemoglobin A level) was obtained from children and adolescents with diagnosis of type 1 diabetes mellitus who were seen at Children's Hospital in New Orleans. A total of 2 mL of blood was also collected and sera were tested for H pylori-specific immunoglobulin G antibodies using an enzyme immunoassay. The daily insulin requirement among infected and uninfected children was compared, and the effect of other variables was evaluated with multiple linear regression. RESULTS: Of the 71 subjects who were evaluated (median age: 11 years), 11 (15.5%) were found to be infected. H pylori infection was more frequent among subjects who were older, who had a lower family income, and who were black. Infected children were found to require more insulin (1.2 vs 0.9 IU/Kg/d) and their glycosylated hemoglobin A level was higher (14.9 vs 11.8) than the level found in uninfected subjects. Multiple linear regression analysis identified H pylori infection duration of illness, race (black), body mass index, and gender (female), to be associated independently with increased daily insulin requirement (IU/kg/d). CONCLUSION: n our study population, children with type 1 diabetes and H pylori infection had an increased daily insulin requirement compared with the requirement of their uninfected peers. The reason for this association requires additional investigation.

Adolescent↗

PubMed2003

L-arginine-mediated vasoreactivity in patients with a risk of stroke.

OBJECTIVES: L-arginine is the substrate for nitric oxide (NO) production and has been shown to induce an endothelium-dependent increase in cerebral blood flow in humans. We studied the hypothesis that L-arginine-mediated vasoreactivity is impaired in patients with cardiovascular risk factors and a risk of stroke. METHODS: 55 patients with cardiovascular risk factors (mean age 63.0 +/- 8.5 years) were included in the study. 45 of them had a history of previous minor stroke or transient ischemic attack (TIA) while 10 patients had cardiovascular risk factors but no previous cerebral ischemic event. Endothelium-dependent changes in cerebral blood flow during the infusion of 30 g L-arginine were assessed by continuous transcranial Doppler sonography of both middle cerebral arteries, intima-media thickness (IMT) of the common carotid artery, by Duplex sonography. Associations between risk factors, IMT, L-arginine reactivity and previous cerebrovascular events were analyzed by stepwise multiple linear regression analysis and patient groups were compared. RESULTS: Normal young volunteers showed an L-arginine-mediated increase in mean flow velocity of 22 +/- 8%; L-arginine reactivity of the 55 patients was 28 +/- 10%. Patients with a history of stroke or TIA had significantly higher flow velocity responses to L-arginine (29 +/- 10%) than patients with cardiovascular risk factors but no previous cerebrovascular event (21 +/- 8%, p < 0.05). Stepwise multiple linear regression analysis showed a significant association of enhanced L-arginine reactivity with previous stroke/TIA (p < 0.001) and elevated fibrinogen levels (p < 0.05) but not with age, IMT, hypertension, cholesterol or other risk factors. The same regression model showed an association between IMT and previous stroke/TIA (p < 0.001) and serum cholesterol levels (p < 0.05) but not L-arginine reactivity. CONCLUSIONS: L-arginine reactivity of the cerebral vessels may be assessed by Doppler sonography and was enhanced in patients with a history of stroke or TIA. It was independent of IMT of the carotid arteries. We conclude that enhanced L-arginine reactivity is a potential marker for cerebral endothelial dysfunction and an independent indicator for an increased risk of stroke.

Aged↗

PubMed2004

Sex hormone-binding globulin is a major determinant of the lipid profile: the PRIME study.

The prevalence of coronary heart disease is much higher in men than in women and sex hormones might play a role in these differences through their influence on the lipid profile. The aim of this cross-sectional study was to study the relationship between hormonal markers (total testosterone (TT), estradiol (E2), sex-hormone-binding globulin (SHBG)) and plasma lipids in a population-based sample. Subjects were 352 men, 50-59 years old, selected in France (Lille, Strasbourg and Toulouse) and Northern-Ireland (Belfast) who had questionnaires and a medical examination at baseline of the PRIME prospective study (1991-1993). Pearson correlation coefficients and Student's t tests were used to identify factors associated with plasma lipids. Multiple linear regression models were used for multivariate analyses, using triglycerides (TG) (log-transformed) and high density-lipoprotein cholesterol (HDL-C) as dependent variables. SHBG and TT were negatively correlated with TG (p<0.0001 and p<0.05, respectively) and positively correlated with HDL-C (p<0.0001 and p<0.01). E2 was positively correlated with TG (p<0.05). No significant association was found between sex-hormones and LDL-C. In multiple linear regression analyses, SHBG remained independently associated negatively with TG (p<0.01) and positively with HDL-C (p<0.0001) after adjustment for centre of recruitment, age, body mass index, systolic blood pressure, smoking, alcohol intake and physical activity. After further adjustment for insulin, the association between SHBG and HDL-C remained highly significant (p<0.0001). The association between SHBG and TG was weakened but remained also significant. Our results suggest that SHBG might to be a central protein in the hormonal regulation of the lipid profile.

Biomarkers↗

PubMedDate not supplied

Serum cholesterol and vitamins A and E in juvenile chronic arthritis.

Serum total cholesterol is decreased during acute infections and in adults with rheumatoid arthritis, probably partly because of enhanced lipid peroxidation. Oxidative stress also causes augmentation of inflammation and tissue damage in arthritic synovium. Therefore, concentrations of serum total cholesterol and the antioxidant vitamins A and E were studied in 125 children with juvenile chronic arthritis. Total serum cholesterol was significantly lower in the patients than in healthy children in most age groups and correlated with the markers of disease activity, haemoglobin and the erythrocyte sedimentation rate. In age- and sex-adjusted stepwise multiple linear regression, serum zinc had a significant predictive value for cholesterol. The vitamin A concentrations in the sera of the patients was virtually the same as in the healthy controls, though serum vitamin E concentrations were low (22.8 +/- 15.2 vs 30.5 +/- 4.3 mumol/l, p less than 0.001). The deficiency in vitamin E was not compensated for by another lipoperoxide antioxidant, glutathione peroxidase. Only serum cholesterol had an independent explanatory significance for vitamin E in multiple linear regression analysis (partial correlation 0.554, p less than 0.001). It is suggested that low vitamin E and impairment of the anti-oxidant protection further contribute to low serum cholesterol values in JCA.

Adolescent↗

PubMed2000

Chemical characteristics and relative bioavailability of supplemental organic zinc sources for poultry and ruminants.

Eight commercially available organic Zn products and reagent-grade ZnSO4 x 7H2O (Zn Sulf) were evaluated by polarographic analysis, and solubility in .1 M K2HPO4-KH2PO4 buffer (pH 5), .2 M HCl-KCl buffer (pH 2), and deionized water. Fractions from these solubility tests were evaluated by gel filtration chromatography for structural integrity. Degree of chelation was generally positively related to chelation effectiveness determined by polarography. The organic sources were Zn methionine complex A (Zn MetA), Zn methionine complex B (Zn MetB), Zn polysaccharide complex (Zn Poly), Zn lysine complex (Zn Lys), Zn amino acid chelate (Zn AA), Zn proteinate A (Zn ProA), Zn proteinate B (Zn ProB), and Zn proteinate C (Zn ProC). Three experiments were conducted to estimate the relative bioavailability of Zn from the organic Zn supplements for chicks and lambs when added at high dietary levels to practical diets. Bone Zn concentration increased (P < .001) as dietary Zn increased in both experiments. When Zn Sulf was assigned a value of 100% as the standard, multiple linear regression slope ratios of bone Zn from chicks fed 3 wk regressed on dietary Zn intake gave estimated relative bioavailability values of 83 +/- 14.6 and 139 +/- 16.9 for Zn AA and Zn ProA, respectively, in Exp. 1 and 94 +/- 11.6, 99 +/- 8.8, and 108 +/- 11.4 for Zn Poly, Zn ProB, and Zn ProC, respectively, in Exp. 2. In Exp. 3, 42 lambs were fed diets containing Zn Sulf, Zn ProA, Zn AA, or Zn MetB for 21 d. Based on multiple linear regression slope ratios of liver, kidney, and pancreas Zn and liver metallothionein concentrations on added dietary Zn, bioavailability estimates relative to 100% for Zn Sulf were 130, 110, and 113 for Zn ProA, Zn AA, and Zn MetB, respectively. Except for Zn ProA, which was greater, the organic Zn supplements had bioavailability values similar to that of Zn Sulf for chicks and lambs. Bioavailability of organic Zn products was inversely related to solubility of Zn in pH 5 buffer in chicks (r2 = .91) and pH 2 buffer in lambs (r2 = .91), but not to an estimate of degree of chelation.

Animal Feed↗

PubMed1996

Differing patterns of mechanical response to direct fetal hormone treatment.

A single combined intramuscular dose of betamethasone and l-thyroxine (T4) or placebo was injected into the shoulder of fetal lambs 48 hours prior to delivery at days 121 (n = 14), 128 (n = 25) or 135 (n = 20) of gestation. Respiratory mechanics were calculated using multiple linear regression analysis. Both respiratory system resistance (RRS) and elastance (ERS) decreased approximately 4 fold between gestational days 121 (D121) and 135 (D135). Both variables were also reduced by hormone treatment. Reduction in ERS was due to a reduction in both lung (EL) and chest wall (EW) components. In absolute terms EW decreased with gestational age; however, EW as a proportion of total elastance (% EW) increased. Inclusion of a volume-dependent elastance term in the multiple linear regression model enabled us to separate total elastance into volume-independent (E1) and volume-dependent (E2V) components. E1 decreased almost 8-fold compared with only a 2.5-fold fall in E2V between D121 and D135. %E2, the proportion of ERS which is volume-dependent and which provides an index of overventilation, doubled over this time period. Hormone treatment affected E1 and E2V components equally hence %E2 was not altered. Both excised lung volume and end expiratory alveolar volume increased with gestational age and with treatment. The response to treatment was qualitatively similar at each of the gestational ages examined, however, for all mechanics variables, except resistance and E1, the magnitude of response to treatment was significantly smaller in D135 animals compared with other age groups.

Airway Resistance↗

PubMed2000

[Factors associated with arterial distensibility in hypertension].

OBJECTIVE: To find out what variables affect changes in arterial compliance in subjects with hypertension by measuring their pulse wave velocity (PWV). DESIGN: Cross-sectional, descriptive study. SETTING: Rural health centre. PATIENTS: 156 hypertense patients under 76, chosen by simple random sampling from those on the hypertension register. MEASUREMENTS AND INTERVENTIONS: We determined the degree of hypertension, years of evolution, systolic pressure (SBP), diastolic pressure (DBP), body mass index (BMI), glucaemia, whether lipaemia existed, diabetes or glucose intolerance, tobacco habit, age, sex and PWV (measured automatically by computer). We performed multivariate analysis by means of multiple linear regression, with PWV as the dependent variable, and age, SBP, DBP, BMI, years of evolution of hypertension, cholesterol, triglycerides and glucaemia as independent variables. RESULTS: Mean age 62.5 (SD 8.8). 28.2% male. Mean SBP 153 (SD 18.9). Mean DBP 87 (SD 10.3). Mean years of evolution 10.4 (SD 7.4). Mean BMI 31.2 (SD 4.9). Hyperglucaemia 24.4%. Mean glucaemia 111.3 (SD 29). Mean PWV 11.82 (SD 2.37). PWV was above the theoretically normal figures in 69.2% of cases. Multiple linear regression showed that the variables which affected PWV significantly were age, SBP and hyperglucaemia. CONCLUSIONS: Arterial compliance can be improved by controlling SBP, given that the other related factors cannot be changed.

Adult↗

PubMed2002

Development of quantitative structure-property relationship models for pseudoternary microemulsions formulated with nonionic surfactants and cosurfactants: application of data mining and molecular modeling.

Data mining, computer-aided molecular modeling, descriptor calculation and multiple linear regression techniques were utilized to produce statistically significant and predictive models for O/W and W/O microemulsions. The literature was scanned over the last 20 years, subsequently, 68 phase diagrams from eight different references were collected. Molecular modeling techniques were then applied on the components of the microemulsion systems to generate plausible 3-D structures. Subsequently, various physicochemical descriptors were calculated based on the resulting 3-D structures. The generated descriptors were correlated with microemulsion existence areas utilizing multiple linear regression analysis (MLR). The generated models were statistically cross-validated and were found to be of significant predictive power. Furthermore, the resulting models allowed better understanding of the process of microemulsion formation.

Drug Compounding↗