SEARCH · PubMed Health

Results for “Linear Regression”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources

PubMed2002

Desorption kinetics of PCP-contaminated soil: effect of temperature.

A thermally enhanced pump-and-treatment method for pentachlorophenol (PCP)-contaminated soil and groundwater has shown potential advantages over the traditional pump-and-treatment method. Studies on the desorption kinetics of PCP from aquifer soil are the first step toward quantitative assessment of the newly proposed method. Five series of desorption batch tests were conducted at different temperatures, and the test results were analyzed by linear regression to determine the best-fit kinetic model for PCP desorbed from the contaminated field soil under all temperature conditions. The first-order kinetic model, parabolic diffusion model, and modified Freundlich model were discussed in linear regression work. A modified Freundlich model was found to describe the PCP desorption kinetics from soil in consideration of a temperature effect.

Absorption↗

PubMed1996

Determinants of heart rate variability.

OBJECTIVES: This study sought to examine clinical determinants of heart rate variability and to report normative reference values for eight heart rate variability measures. BACKGROUND: Although the clinical implications of heart rate variability have been described, clinical determinants and normative values of heart rate variability measures have not been studied systematically in a large community-based population. METHODS: The first 2 h of ambulatory electrocardiographic recordings obtained in Framingham Heart Study subjects attending a routine examination were reprocessed for heart rate variability. Recordings with transient or persistent nonsinus rhythm, premature beats > 10% of total beats, < 1-h recording time or processed time < 50% of recorded time were excluded; subjects receiving antiarrhythmic medications also were excluded. Among five frequency domain and three time domain measures that were obtained, low frequency power (0.04 to 0.15 Hz), high frequency power (0.15 to 0.40 Hz) and the standard deviation of total normal RR intervals based on 2-h recordings were selected for the principal analyses. Variables with potential physiologic effects or possible technical influences on heart rate variability measures were chosen for multiple linear regression analysis. Normative values, derived from a subset of healthy subjects, were adjusted for age and heart rate. RESULTS: There were 2,722 eligible subjects with a mean age (+/-SD) of 55 +/- 14 years. Three separate multiple linear regression analyses revealed that higher heart rate, older age, beta-adrenergic blocking agent use, history of myocardial infarction or congestive heart failure, diuretic use, diastolic blood pressure > or = 90 mm Hg, diabetes mellitus, consumption of three or more cups of coffee per day and smoking were associated with lower values of one or more heart rate variability measures, whereas longer processed time, start time in the morning, frequent supraventricular and ventricular premature beats, female gender and systolic blood pressure > or = 160 mm Hg were associated with higher values. Age and heart rate were the major determinants of all three selected heart rate variability measures (partial R2 values 0.125 to 0.389). Normative reference values for all eight heart rate variability measures are presented. CONCLUSIONS: Age and heart rate must be taken into account when assessing heart rate variability.

Adult↗

PubMed2003

Effect of central corneal thickness on surgically induced astigmatism in cataract surgery.

PURPOSE: To evaluate the effect of central corneal thickness (CCT) on surgically induced astigmatism (SIA) in cataract surgery using temporal clear corneal incisions. SETTING: Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea. METHODS: The retrospective nonrandomized clinical study comprised 129 eyes that had cataract surgery performed through a sutureless temporal clear corneal incision. Eyes were categorized according to the axis of the preoperative astigmatism: against the rule (ATR, 0 to 45 degrees; n = 64) or with the rule (WTR, 46 to 90 degrees; n =65). Corneal topography was taken preoperatively and 1 day and 2 months postoperatively to evaluate the change in the cornea. The SIA was calculated using the polar method from simulated keratometric readings obtained with topography. Correlations between SIA and CCT were analyzed by linear regression analysis and compared between the ATR and the WTR groups. RESULTS: One day postoperatively, the SIA was negatively correlated with CCT in the ATR group but not in the WTR group (P =.050 versus P =.92; linear regression analysis). At 2 months, the correlation between CCT and SIA was no longer statistically significant. CONCLUSIONS: Central corneal thickness was negatively correlated with the amount of SIA immediately postoperatively when the preoperative astigmatism was ATR. The correlation was not present 2 months after surgery. These results may be applied to abnormally thin corneas such as those after keratorefractive surgery.

Aged↗

PubMedDate not supplied

Associations between specific measures of vision and vision-related quality of life in patients with bothnia dystrophy, a defined type of retinitis pigmentosa.

PURPOSE: To assess the relationship between objective tests of visual function and vision-related quality of life in patients with Bothnia dystrophy (BD), a retinal dystrophy of retinitis pigmentosa type with progressive maculopathy. METHODS: Forty-nine patients were tested. Weighted distance logMAR visual acuity (WVA), weighted logMAR low contrast VA (WCS), and binocular visual field (VF) areas were calculated. Vision-related quality of life (VRQL) was assessed using the 25-item National Eye Institute-Visual Function Questionnaire (NEI-VFQ-25). Correlation statistics were used and adjusted analyses of the relationship between the composite score and the objective visual function tests were performed with multiple linear regression. RESULTS: VRQL was significantly correlated with age, WVA, WCS, and binocular VF areas (P < 0.001). Calculation of partial correlation coefficients showed age to be significantly correlated only with VF (V-4-e) area (P < 0.0001). Multiple linear regression analyses revealed age and WVA to be significantly associated with the NEI-VFQ-25 composite score (P < 0.02 and P = 0.001, respectively). WVA alone was the strongest predictor of self-reported experience of total visual function in BD patients (r 2= 0.69). CONCLUSIONS: A strong relationship between objective tests of visual function and patient perceived VRQL as assessed by a questionnaire was found. WVA was the strongest predictor and together with age explained almost 70% of the variability of the composite score of the questionnaire.

Adolescent↗

PubMed1980

The binding of oxidised coenzyme to bovine-liver glutamate dehydrogenase studied by circular-difference spectroscopy.

1. The binding of NAD+ to glutamate dehydrogenase may be followed quantitatively by titration, using high-sensitivity circular dichroism (CD) difference spectroscopy. 2. The CD of the bound coenzyme in the binary complex E . NAD closely resembles that of bound ADP, although the affinity is much lower, being 350-fold less for NAD+ at 20 degrees C in 0.1 M phosphate, pH 7. 3. A family of CD spectra may be analysed by unconstrained linear regression assuming only three components: free enzyme, free coenzyme, and a single binary complex, E . NAD. 4. Taking the molar CD of bound ADP as representing the molar CD of the adenine chromophore of bound NAD+, the linear regression shows the formation of a simple 1 : 1 complex E . NAD with Kd = 0.72 mM in a simple binding process without positive or negative cooperativity. 5. NADP+ binding is more than 10-fold weaker than NAD+ binding. 6. From the similarity of the CD of bound ADP and bound NAD+ it is probable that NAD+, in forming a simple binary complex, binds preferentially at the regulatory (adenine nucleotide) binding site (site II). 7. Direct evidence has been obtained for the binding of a second molecule of NAD+ to the ternary complex E . NAD . glutarate. This process occurs with low affinity and is probably also located at the adenine regulatory site. 8. This second-site binding of NAD+ may contribute to the phenomena of non-Michaelis-Menten kinetics and apparent negative homotropic interactions in the binding of NAD+, previously attributed to subunit-subunit cooperative interactions.

Adenosine Diphosphate↗

PubMed1992

Use of non-invasive finger blood pressure monitoring in the estimation of aortic pressure at rest and during the Mueller manoeuvre.

The aim of this investigation was to evaluate whether reliable estimates of aortic pressure can be derived using non-invasive finger blood pressure monitoring. Finger blood pressure (Ohmeda 2300 Finapres device; Finapres, Englewood, CO) was compared with simultaneous ascending aortic pressure measured with a catheter-transducer system both at rest and during acute negative intrathoracic pressure (the Mueller manoeuvre). Thirty-eight patients aged 17-73 years were studied. All were undergoing routine diagnostic or therapeutic cardiac catheterization. Beat-to-beat values of systolic, diastolic and mean non-invasive finger and invasive aortic blood pressure were measured at rest and factors which might have an influence on the difference between methods were examined. The mean finger-aortic difference was +5 +/- 14 mmHg for systolic, -2 +/- 7 mmHg for diastolic, -5 +/- 8 mmHg for mean and +6 +/- 13 mmHg for pulse pressure. In multivariate linear regression analysis, the difference in systolic pressure was related to aortic systolic pressure (standardized coefficient beta = -0.33, P = 0.01), heart rate (beta = 0.49, P < 0.000), age (beta = -0.29, P < 0.025) and height (beta = 0.40, P < 0.005). The linear regression equations to derive resting aortic pressures from the non-invasive finger pressure readings had correlation coefficients between 0.83 and 0.87 and standard errors of estimate between 6 and 14 mmHg. During the Mueller manoeuvre, Finapres reproduced average pressure changes reliably compared with intra-aortic pressure. Due to moderate inter-individual variation in the finger-aortic differences the correlation coefficients ranged from 0.83 to 0.93 and the standard errors of estimate from 3 to 6 mmHg. Non-invasive finger blood pressure monitoring could be used to estimate central aortic mean and diastolic blood pressure fairly reliably at rest, but with respect to systolic pressure the variance in finger-aortic difference was marked. The average intra-aortic pressure changes caused by the Mueller manoeuvre were reliably reproduced by the Finapres device.

Adolescent↗

PubMed1980

The development of lampbrush chromosome-type transcription in the early diplotene oocytes of Xenopus laevis: an electron-microscope analysis.

Oocytes of Xenopus laevis in pachytene and early diplotene of meiosis have been studied using the Miller spreading technique. Transcription first appears in germinal vesicles 25-40 micrometers in diameter, when the oocyte is in early diplotene. Transcription at this stage consists of arrays of short RNP transcripts, irregularly distributed along the DNP axis. Linear regression analysis has shown that many of these arrays are transcription units (Type I) with the transcripts having a common point of origin. The lengths of these early transcription units (mean = 7.06 +/- 5.06 micrometers), calculated from the linear regression data, are comparable to the lengths of transcription units from later stages, including Dumont stage 3. The polymerase granules of Type I transcription units are widely and irregularly spaced, having a mean spacing of 505 +/- 748 nm. More advanced transcription units (Type II, mean length = 8.72 +/- 3.77 micrometer) are usually found in the same chromosome set as the Type I units. Type II transcription units have closer and more regularly spaced polymerase granules than Type I transcription units (mean spacing = 92 +/- 49 nm). Both Type I and II transcription units have comparatively short RNP transcripts, the mean values for the slopes of their regression lines being 0.1336 and 0.1440 respectively. By the time the germinal vesicles are about 50-60 micrometers in diameter the transcription units have a quite different morphology (Type III). The lengths of the Type III transcription units are comparable to the Type I and II units, the mean length being 6.34 +/- 4.03 micrometers. The spacing of the polymerase granules in the Type III units is closer and more regular than the earlier stages (70 +/- 40 nm). Another significant difference between Type III and Types I and II transcription units is a decrease in the foreshortening of the Type III RNP transcripts. The mean slope of the regression lines for Type III transcription units is 0.2439. The morphological appearance of the Type III transcription unit is virtually identical to that of the transcription units from Dumont stage 3 oocytes, both with respect to the length and the spacing of the polymerase granules. However, the transcripts in Type III transcription units are still more foreshortened than those of Dumont stage 3 oocytes, having mean regression slopes of 0.4728. From the data obtained in the present study, it has been concluded that the pattern of lampbrush-type transcription is virtually fully established by the time most germinal vesicles are about 50 micrometers in diameter.

Animals↗

PubMed2003

Concurrent validation of the OMNI perceived exertion scale for resistance exercise.

UNLABELLED: The criterion variables were total weight lifted (Wttot ) determined separately for women and men during BC and KE, and blood lactic acid concentration ([Hla]) determined for a combined female ( N = 10) and male ( N = 10) subset during BC. Subjects performed three separate sets of 4, 8, and 12 repetitions for BC and KE at 65% one-repetition maximum. Rating of perceived exertion for the active muscles (RPE-AM) was measured during the mid and final repetition and RPE for the overall body (RPE-O) during the final repetition. : For both female and male groups across the three sets: (a) RPE-AM ranged from 3.6 to 8.2 for BC and 5.1 to 9.6 for KE and (b) RPE-O ranged from 2.4 to 6.7 for BC and 4.2 to 7.6 for KE. Positive linear regressions ranged from r = 0.79 to 0.91 ( P < 0.01) between Wttot and RPE-AM (mid), RPE-AM (final), and RPE-O for both BC and KE in both sex groupings. A positive ( P < 0.01) linear regression was found between [Hla] and RPE-AM (final) (r = 0.87) during BC. RPE did not differ between women and men at any measurement point within each set for BC and KE. RPE-AM (final) was greater ( P < 0.01) than RPE-O in the three sets of BC and KE. CONCLUSION: Findings provided concurrent validation of the OMNI-RES to measure RPE for the active muscle and overall body in young recreationally trained female and male weight lifters performing upper- and lower-body resistance exercise.

Adolescent↗

PubMed2000

Exposure measurement error in time-series studies of air pollution: concepts and consequences.

Misclassification of exposure is a well-recognized inherent limitation of epidemiologic studies of disease and the environment. For many agents of interest, exposures take place over time and in multiple locations; accurately estimating the relevant exposures for an individual participant in epidemiologic studies is often daunting, particularly within the limits set by feasibility, participant burden, and cost. Researchers have taken steps to deal with the consequences of measurement error by limiting the degree of error through a study's design, estimating the degree of error using a nested validation study, and by adjusting for measurement error in statistical analyses. In this paper, we address measurement error in observational studies of air pollution and health. Because measurement error may have substantial implications for interpreting epidemiologic studies on air pollution, particularly the time-series analyses, we developed a systematic conceptual formulation of the problem of measurement error in epidemiologic studies of air pollution and then considered the consequences within this formulation. When possible, we used available relevant data to make simple estimates of measurement error effects. This paper provides an overview of measurement errors in linear regression, distinguishing two extremes of a continuum-Berkson from classical type errors, and the univariate from the multivariate predictor case. We then propose one conceptual framework for the evaluation of measurement errors in the log-linear regression used for time-series studies of particulate air pollution and mortality and identify three main components of error. We present new simple analyses of data on exposures of particulate matter < 10 microm in aerodynamic diameter from the Particle Total Exposure Assessment Methodology Study. Finally, we summarize open questions regarding measurement error and suggest the kind of additional data necessary to address them.

Air Pollution↗

PubMed1991

Ventilatory lung function in young cigarette smokers: a study of susceptibility.

The objective of this study was to estimate the effect of cigarette smoking on ventilatory lung function among young adults with special emphasis on the recognition of susceptible subgroups. In a cross-sectional study of 1,044 adults aged 15-40 yrs, a statistically significant linear relationship between quantity of smoking in cigarette-years and level of forced expiratory volume in one second (FEV1) was found. Among current cigarette smokers, FEV1 level was on average 35 ml lower for each 100 cigarette-years of exposure (corresponding to smoking of ten cigarettes per day for 10 yrs) compared to lifelong nonsmokers in a linear regression adjusted for confounding. Potentially susceptible subgroups were studied by introducing interaction terms between quantitative smoking and gender, wheezing, atopy, asthma, childhood respiratory illness and exposure to environmental tobacco smoke during the growth period, to the additive linear regression model explaining the FEV1 level. Wheezing was found to modify the effect of smoking significantly: the FEV1 level was on average 68 ml lower for each 100 cigarette-years due to interaction between smoking and wheezing. An introduction of the interaction term eliminated the independent effect of smoking. The results suggest that the detrimental effect of smoking on FEV1 in young adults may be limited to individuals with wheezing. Thus, the presence of wheezing among smokers indicates a higher risk for low level of ventilatory lung function compared to smokers who do not wheeze.

Adolescent↗

PubMedDate not supplied

Accuracy of clinical estimates of tumor dimensions. A clinical-pathologic correlation study of posterior uveal melanomas.

The authors reviewed the clinical records of 50 patients who underwent enucleation for posterior uveal malignant melanoma to determine the correlation between clinical estimates of tumor size made prior to enucleation and pathologic measurements made during gross examination. Linear regression of the pathologic measurements of several tumor dimensions on the corresponding clinical estimates documented correlation coefficients ranging from 0.81 for minimal basal diameter to 0.92 for tumor thickness. Although these values suggest a high level of linear correlation, wide confidence limits indicate a significant level of random variation in the data points. Further, nonzero intercepts and nonunity slopes of the linear regression lines indicate a systematic variation between clinical estimates and gross pathologic measurements of tumor size.

Humans↗

PubMed2001

Analysis of survival of young and old Aedes aegypti (Diptera: Culicidac) from Puerto Rico and Thailand.

It generally is assumed that the daily probability of survival of wild adult mosquitoes is independent of age. To test this assumption we conducted mark-release-recapture studies in Puerto Rico and Thailand to determine if estimated daily survival rates between two different age cohorts of the dengue vector Aedes aegypti (L.) were the same. Survivorship was estimated with nonlinear regression analysis using bootstrapping to obtain estimates of errors. Initial recapture success of the younger cohort was greater than the older cohort at both locations. Our analysis revealed a significantly greater survival rate for the younger cohort of females in Puerto Rico, and no significant differences between age cohorts in Thailand. For comparison, a traditional approach for analyzing these type of data, linear regression of log-transformed captures over time (exponential model), was used to calculate the probability of daily survival based on slopes of linear regression lines for recaptured mosquitoes. With this method, the estimated daily survival rate of older females (13-23 d old) was significantly greater than survival of younger ones (3-13 d old) in Puerto Rico and Thailand. In addition, short-range movement of mosquitoes was observed in Puerto Rico; maximum dispersal distance detected was 79 m. Survival rates of adult Ae. aegypti may be age-dependent and nonlinear regression analysis is a sensitive approach for comparing patterns of mosquito survival based on mark, single release, multiple recapture data.

Aedes↗

PubMed2004

Defining a radiotherapy target with positron emission tomography.

PURPOSE: F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) imaging is now considered the most accurate clinical staging study for non-small-cell lung cancer (NSCLC) and is also important in the staging of multiple other malignancies. Gross tumor volume (GTV) definition for radiotherapy, however, is typically based entirely on computed tomographic data. We performed a series of phantom studies to determine an accurate and uniformly applicable method for defining a GTV with FDG-PET. METHODS AND MATERIALS: A model-based method was tested by a phantom study to determine a threshold, or unique cutoff of standardized uptake value based on body weight (standardized uptake value [SUV]) for FDG-PET based GTV definition. The degree to which mean target SUV, background FDG concentration, and target volume influenced that GTV definition were evaluated. A phantom was constructed consisting of a 9.0-L cylindrical tank. Glass spheres with volumes ranging from 12.2 to 291.0 cc were suspended within the tank, with a minimum separation of 4 cm between the edges of the spheres. The sphere volumes were selected based on the range of NSCLC patient tumor volumes seen in our clinic. The tank and spheres were filled with a variety of known concentrations of FDG in several experiments and then scanned using a General Electric Advance PET scanner. In the initial experiment, six spheres with identical volumes were filled with varying concentrations of FDG (mean SUV = 1.85 approximately 9.68) and suspended within a background bath of FDG at a similar concentration to that used in clinical practice (0.144 muCi/mL). The second experiment was identical to the first, but was performed at 0.144 and 0.036 muCi/mL background concentrations to determine the effect of background FDG concentration on sphere definition. In the third experiment, six spheres with volumes of 12.2 to 291.0 cc were filled with equal concentrations of FDG and suspended in a standard background FDG concentration of 0.144 muCi/mL. Sphere images in each experiment were auto-contoured (simulating a GTV) using the threshold SUV that yielded a volume matching that of the known sphere volume. A regressive function was constructed to represent the relationship between the threshold SUV and the mean target SUV. This function was then applied to define the GTV of 15 NSCLC patients. The GTV volumes were compared to those determined by a fixed image intensity threshold proposed by other investigators. RESULTS: There was a strong linear relationship between the threshold SUV and the mean target SUV. The linear regressive function derived was: threshold SUV = 0.307 x (mean target SUV) + 0.588. The background concentration and target volume indirectly affect the threshold SUV by way of their influence on the mean target SUV. We applied the linear regressive function, as well as a fixed image intensity threshold (42% of maximum intensity) to the sphere phantoms and 15 patients with NSCLC. The results indicated that a much smaller deviation occurred when the threshold SUV regressive function was utilized to estimate the phantom volume as compared to the fixed image intensity threshold. The average absolute difference between the two methods was 21% with respect to the true phantom volume. The deviation became even more pronounced when applied to true patient GTV volumes, with a mean difference between the two methods of 67%. This was largely due to a greater degree of heterogeneity in the SUV of tumors over phantoms. CONCLUSIONS: An FDG-PET-based GTV can be systematically defined using a threshold SUV according to the regressive function described above. The threshold SUV for defining the target is strongly dependent on the mean target SUV of the target, and can be uniquely determined through the proposed iteration process.

Body Weight↗

PubMed2004

Estimating the degree of emergency department overcrowding in academic medical centers: results of the National ED Overcrowding Study (NEDOCS).

OBJECTIVES: No single universal definition of emergency department (ED) overcrowding exists. The authors hypothesize that a previously developed site-sampling form for academic ED overcrowding is a valid model to quantify overcrowding in academic institutions and can be used to develop a validated short form that correlates with overcrowding. METHODS: A 23-question site-sampling form was designed based on input from academic physicians at eight medical schools representative of academic EDs nationwide. A total of 336 site-samplings at eight academic medical centers were conducted at 42 computer-generated random times over a three-week period by independent observers at each site. These sampling times ranged from very slow to severely overcrowded. The outcome variable was the degree of overcrowding as assessed by the charge nurse and ED physicians. The full model consisted of objective data that were obtained by counting the number of patients, determining patients' waiting times, and obtaining information from registration, triage, and ancillary services. Specific objective data were indexed to site-specific demographics. The outcome and objective data were compared using a multiple linear regression to determine predictive validity of the full model. A five-question reduced model was calculated using a backward stepdown procedure. Predictive validity and relationships between the outcome and objective data were assessed using a mixed-effects linear regression model, treating center as random effect. RESULTS: Overcrowding occurred 12% to 73% of the time (mean, 35%), with two hospitals being overcrowded more than 50% of the time. Comparison of objective and outcome data resulted in an R(2) of 0.49 (p < 0.001), indicating a good degree of predictive validity. A reduced five-question model predicted the full model with 88% accuracy. CONCLUSIONS: Overcrowding varied widely between academic centers during the study period. Results of a five-question reduced model are valid and accurate in predicting the degree of overcrowding in academic centers.

Academic Medical Centers↗

PubMed2000

Predicting population dental disease experience at a small area level using Census and health service data.

BACKGROUND: Information on the dental disease patterns of child populations is required at a small area level. At present, this can be provided only by expensive whole population surveys. The aim of this study was to evaluate the ability of Census data combined with health service information to provide estimates of population dental disease experience at the small area level. METHOD: Clinical dental data were collected from a large cross-sectional survey of 5-year-old children. A preliminary series of bivariate linear regression analyses were undertaken at ward level with the mean number of decayed, missing or filled teeth per child (dmft) as the dependent variable, and the Census and health service and lifestyle variables suspected of having a strong relationship with dmft as independent variables. This was followed by fitting a multiple linear regression model using a stepwise procedure to include independent variables that explain most of the variability in the dependent variable dmft. RESULTS: All deprivation indicators derived from the Census showed a highly significant (p<0.001) bivariate linear relationship with ward dmft. The Jarman deprivation score gave the highest R2 value (0.45), but the Townsend index (R2=0.43) and the single Census variable 'percentage of households with no car' (R2 = 0.42) gave very similar results. The health and lifestyle indicators also showed highly significant (p<0.001) linear relationships with dmft. The R2 values were generally much lower than the deprivation-related Census variables, with the exception of the percentage of residents who smoked (R2 = 0.42). None of the health or lifestyle variables was included in the final dental disadvantage model. This model explained 51 per cent of the variability of ward dmft. CONCLUSIONS: The results demonstrate the strong relationship between dental decay and deprivation, and all of the commonly used measures of deprivation exhibited a similar performance. For this population of young children health and health services shelf data did not improve on the ability of deprivation-related Census variables to predict population dental caries experience at a small area level.

Child, Preschool↗

PubMed2006

Soft tissue to hard tissue advancement ratios for mandibular elongation using distraction osteogenesis in children.

Distraction osteogenesis is extensively used for the elongation of hypoplastic mandibles in children, yet the soft tissue profile response to this is not well understood. The pre- and posttreatment lateral cephalometric radiographs of 27 pediatric patients who underwent bilateral mandibular elongation using distraction osteogenesis were analyzed retrospectively to correlate horizontal soft tissue advancement with horizontal underlying bone advancement at B point and pogonion. Horizontal advancement (in millimeters) of bone and overlying soft tissue at these points was collected from the radiographs of each patient, and linear regression analysis was performed to determine the relationship of hard to soft tissue horizontal advancement at these points. A 1:0.90 mean ratio of bone to soft tissue advancement was observed at B point/labiomental sulcus and at pogonion/soft tissue pogonion (linear regression analysis demonstrated slopes [beta1 values] of 0.94 and 0.92, respectively). These ratios were consistent throughout the sample population and are highly predictive of the soft tissue response that can be anticipated. Magnitude of advancement, age, and sex of the patient had no effect on these ratios in our population. This study assists with our understanding of the soft tissue response that accompanies bony elongation during distraction osteogenesis which will allow us to more effectively treatment plan the orthodontic and surgical intervention that will optimize the patients' functional and esthetic outcome.

Adolescent↗

PubMed2000

Waist circumference and sagittal diameter reflect total body fat better than visceral fat in older men and women. The Health, Aging and Body Composition Study.

The validity of waist circumference and sagittal diameter as surrogate measures of visceral fat were assessed using preliminary cross-sectional data from the Health, Aging and Body Composition Study, a cohort of 3,075 men and women aged 70-79. Weight, body mass index, waist circumference, waist/thigh ratio, and sagittal diameter were compared by correlation, graphical analysis, and regression to total body fat as measured by dual-energy X-ray absorptiometry (Hologic 4500A), and to visceral fat area as measured by computerized tomography. We included 2,830 persons, 1,439 women and 1,391 men with complete data on all measurements. For both men and women, all measurements were strongly correlated with both total body fat and visceral fat except the waist/thigh ratio. However, waist circumference, sagittal diameter, weight, and body mass index were more closely related to total body fat than to visceral fat area (R2 for the linear regression of waist circumference on total body fat was 0.69 in women and men; R2 for linear regression of waist circumference on visceral fat area was 0.40 in women, and 0.49 in men). These data suggest that the contribution of visceral fat to health risks will be better assessed by directly measuring this fat depot.

Adipose Tissue↗

PubMed2003

Insulin-like growth factor-I and its binding proteins in colostrum compared to measures in serum of Holstein neonates.

Colostral insulin-like growth factor-I (IGF-I) may be beneficial in the development of gastrointestinal tracts of bovine neonates. Thus, the purpose of this study was to examine relationships among concentrations of IGF-I and IGF-binding proteins (IGFBP) in colostrum used at two initial feedings and serum concentrations of IGF-I, IGFBP, total protein, gamma glutamyltransferase (GGT), and immunoglobulin G at 0 and 48 h after birth in Holstein neonates. Calves (n = 22) were separated from dams immediately after birth. Blood samples were taken before initial feeding and at 48 h after birth. Calves were fed 2 L of colostrum twice and milk replacer thereafter. Linear regression of serum IGF-I at 48 h and colostral IGF-I revealed a significant positive relationship (R2 = 0.204). Serum IGFBP-3 at 48 h and colostral IGFBP-3 also had a positive relationship (R2 = 0.143). However, linear regression of colostral IGF-I on the difference in serum IGF-I at 48 and 0 h was not significant. Calves were assigned to group 1 (0-h serum IGF-I < 10 ng/ml; n = 11) or group 2 (0-h serum IGF-I > or = 10 ng/ml; n = 11) for further analysis. There were no differences in serum IGF-I or IGFBP-2, -3, -4, and -5 concentrations at 48 h between groups 1 and 2. Correlation coefficients revealed negative relationships of serum IGF-I at 0 h to the difference between serum IGF-I at 48 and 0 h (r = -0.824), as well as birth weight of the calf to the amount of GGT at 48 h (r = -0.604). Females had lower birth weights than males, but sex of calf did not affect serum measures. At 0 h, but not 48 h, total serum protein was correlated to serum GGT concentrations (r = 0.573). From indirect evidence, absorption of colostral IGF-I and IGFBP-3 into systemic circulation may occur, but relative importance compared to endogenous sources is uncertain.

Animals↗