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PubMed1998

Linear O2 use-pressure-volume area relation from curved end-systolic pressure-volume relation of the blood-perfused rat left ventricle.

We measured rat left ventricular pressure, volume, and oxygen consumption ( = arteriovenous oxygen content differencexcoronary flow) to establish a new evaluation of its mechanoenergetics in the whole heart preparation by using the cross-circulation method. We obtained a curved end-systolic pressure-volume relation in contrast to a linear end-systolic pressure-volume relation in dogs, rabbits, and humans. However, we obtained a linear oxygen consumption per beat (VO2)-systolic pressure-volume area (PVA, a measure of left ventricular total mechanical energy per beat) relation as in other species. Thus PVA can be a good index for assessing rat left ventricular mechanoenergetics. The VO2 intercept and slope of the linear VO2-PVA relation correspond to those in other species. Intracoronary calcium elevated the curved end-systolic pressure-volume relation and significantly increased PVA at 0.15 ml/g of left ventricular end-diastolic volume (PVA0.15) by 50%. Calcium also significantly increased the VO2 intercept of the VO2-PVA relation by 30% without a change in its slope. We conclude that the rat left ventricular end-systolic pressure-volume relation is curved, but the VO2-PVA relation is linear, and that the VO2 intercept is mainly composed of PVA-independent VO2, presumably VO2 for Ca2+ handling in the excitation-contraction coupling and basal metabolism. Therefore we propose PVA at an appropriate left ventricular volume and the VO2 intercept as good rat left ventricular mechanoenergetic indexes despite the nonlinearity of the end-systolic pressure-volume relation.

Animals↗
PubMed1996

Representation of perceptual dimensions of insect prey during terminal pursuit by echolocating bats.

The echolocating big brown bat, Eptesicus fuscus, broadcasts brief frequency-modulated (FM) ultrasonic sounds and perceives objects from echoes of these sounds returning to its ears. Eptesicus is an insectivorous species that uses sonar to locate and track flying prey. Although the bat normally hunts in open areas, it nevertheless is capable of chasing insects into cluttered environments such as vegetation, where it completes interceptions in much the same manner as in the open except that it has to avoid the obstacles as well as catch the insect. During pursuit, the bat shortens its sonar signals and increases their rate of emission as it closes in to seize the target, and it keeps its head pointed at the insect throughout the maneuver. In the terminal stage of interception, the bat makes rapid adjustments in its flight-path and body posture to capture the insect, and these reactions occur whether the bat is pursuing its prey in the open or close to obstacles such as vegetation. Insects can be distinguished from other objects by the spectrum and phase of their echoes, and Eptesicus is very good at discriminating these acoustic features. To identify the insect in the open, but especially to distinguish which object is the insect in clutter, the bat must have some means for representing these features throughout the interception maneuver. Moreover, continuity for perception of these features is necessary to keep track of the prey in complex surroundings, so the nature of the auditory representations for the spectrum and phase of echoes has to be conserved across the approach, tracking, and terminal stages. The first problem is that representation of changes in the phase of echoes requires neural responses in the bat's auditory system to have temporal precision in the microsecond range, which seems implausible from conventional single-unit studies in the bat's inferior colliculus, where the temporal jitter of responses typically is hundreds of microseconds. Another problem is that echoes do not explicitly evoke neural responses in the inferior colliculus distinct from responses evoked by the broadcast during the terminal stage because the delay of echoes is too short for responsiveness to recover from the emissions. In contrast, each emission and each echo evokes its own responses during the approach and tracking stages of pursuit. How does the bat consistently represent the phase of echoes in spite of these evident limitations in neural responses? Local multiunit responses recorded from the inferior colliculus of Eptesicus reveal a novel format for encoding the phase of echoes at all stages of interception. Changes in echo phase (0 degree or 180 degrees) produce shifts in the latency of responses to the emission by hundreds of microseconds, an unexpected finding that demonstrates the existence of expanded time scales in neural responses representing the target at all stages of pursuit.

Animals↗
PubMed1994

Factors affecting calculation and use of conversion equations for genetic merit of dairy bulls.

Factors affecting calculation and use of conversion equations were reviewed. Methods of expressing reliability of converted evaluations were surveyed. Of 16 countries responding, 6 did not calculate reliability for converted evaluations, 5 accepted reliability from the exporting country, and 5 assumed genetic correlations of .6 to 1.0 with the US. Genetic correlations between the US and 8 other countries were estimated and generally were > or = .9; estimated correlations between the US and Canada were 1.0. Estimated correlations averaged .93 for milk, .89 for fat, and .92 for protein yields. Correlation estimates were lowest for countries differing most from the US in management conditions (Australia, New Zealand) or trait definition (Germany), which suggests that correlation estimates < 1.0 indicate differences in trait measurement as well as differences in biological expression. Conversion equations were computed from data of US and Canadian Holstein bulls with and against the gene flow. Equations against the gene flow generally had regression coefficients and intercepts lower than those calculated with the gene flow. Lower regression coefficients were explained by selection on the dependent variable. Lower intercepts were attributed to preferential treatment of daughters from imported semen, which would lower intercepts for equations against the gene flow and inflate intercepts with the gene flow.

Animals↗
PubMed1998

Influences of progeny test programs on genetic evaluations of young sires.

Our purpose was to examine differences among AI progeny test programs in their effectiveness in identifying elite young sires for milk and protein. Data were from 6238 Holstein sires in five animal model evaluations of the USDA from January 1995 to February 1997. Bulls were required to be < or = 8 yr of age and to have > or = 10 daughters in production at the time of the evaluation. Bulls in AI programs were placed in nine groups based on affiliation with major AI organizations; from these nine groups, bulls with daughters averaging < 150 DIM and bulls sampled in > 100 herds were placed in two separate groups. Bulls sampled in organizations with controller numbers > or = 30 and bulls that had no connection to a sampling organization formed two additional groups. We also classified bulls by sampling codes of the National Association of Animal Breeders. A model predicting daughter yield deviation included effects of organization or sampling code, parent average (free of progeny information), and the interaction of organization or sampling method and parent average. When all data were used, a common intercept for milk was appropriate for all sampling methods, but the slopes differed (R2 = 0.44). Neither a common intercept nor a common slope was appropriate for protein. When data were restricted to the nine major organizations, a common intercept and slope were appropriate for milk, and R2 decreased to 0.14. A common intercept and slope were found for protein, and R2 decreased to 0.15. We detected no important differences in response to pedigree selection among progeny-testing methods used by major organizations that provide semen, but a difference was detected among the sampling codes of the National Association of Animal Breeders.

Animals↗
PubMed1989

Magnitude estimates for electrical pulses: evidence for two neural mechanisms.

The hypothesis that there are two neural mechanisms for electrocutaneous stimulation--one that is sensitive to low current and is adaptive to repeated stimulation and another that is responsive to high current and is less adaptive--was tested in a control and four main experiments. In the main experiments, magnitude estimates obtained for single electrical pulses (of 2-msec duration) were described by a simple power function for each combination of high- and low-current levels and 10 trial blocks. The results were: (1) The slope of the power function for low current was steeper than was that for high current; (2) for low current, the intercept of the power function decreased with increasing block, whereas for high current, it remained constant over blocks; (3) this decrease of the intercept for low current disappeared when judgmental blocks were separated by a rest period of 8 min; (4) the modulus did not affect the slope; (5) for a large modulus combined with low current, the intercept decreased rapidly over trial blocks, whereas for a small modulus combined with high current, the intercept increased over trial blocks. The first four findings support the two-mechanism hypothesis, but the last one may also be interpretable in terms of the regression to absolute scale values.

Adolescent↗
PubMed2000

Proposed flow cytometric reference method for the determination of erythroid F-cell counts.

BACKGROUND: Quantitation of adult erythrocytes (RBC) containing fetal hemoglobin (F cells) is of potential clinical utility in evaluating erythropoietic disorders, such as myelodysplasia and hemoglobinopathies, and in monitoring F-cell augmenting therapy. F-cell counting methodologies include fluorescence microscopy and flow cytometry. Previous flow cytometric methods have employed an isotype antibody control to distinguish F cells from non-F cells. We investigated the feasibility of using the orange autofluorescence signal (FL2) in glutaraldehyde-fixed RBC to substitute for fluorescein isothiocyanate (FITC)-labeled isotype control antibody use in F-cell quantitation. METHODS: Our previously published method for fetal red cell detection in fetomaternal hemorrhage was used, employing a FITC-labeled anti-hemoglobin F (HbF) monoclonal antibody reagent. Blood samples with varying F-cell counts were quantitated for F cells using both immunofluorescence microscopy and flow cytometry comparing FITC-labeled isotype to FL1 thresholding defined by FL2 autofluorescence. RESULTS: F cell percentages obtained by using an FL2 defined threshold for FL1 gating correlated well with expected values in diluted blood samples (r(2) = 0.994, slope = 1. 019, intercept = 0.24), values obtained using an isotype control (r(2) = 0.996, slope = 1.012, intercept = -0.17), and microscopic immunofluorescence counts (r(2) = 0.989, slope = 0.999, intercept = -0.72). F-cell quantitation by the isotype control and FL2 autofluorescence methods was also comparable in 40 blood samples (r(2) = 0.994, slope = 1.014, intercept = 0.03). Intra-assay, interobserver, and interinstrument precision with this autofluorescence gating method exhibited low imprecision (coefficient of variation <14%). CONCLUSION: This novel method is a more objective and less laborious alternative for F-cell quantitation by flow cytometry compared to using an isotype control or microscopy, thereby providing a more robust methodology for clinical studies and consideration as a laboratory reference method for F-cell counting.

Adult↗
PubMed2004

[Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles].

OBJECTIVE: Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles. METHODS: Thirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts. RESULTS: EMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05). CONCLUSION: Repetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.

Adult↗
PubMed1989

Elective response to propranolol or verapamil in ischemia on effort.

Twenty-four patients with effort angina and positive exercise stress test performed four control exercise stress tests, two tests while taking propranolol (240 mg/day) and two tests while taking verapamil (320 mg/day), in a randomized crossover sequence. For each test the following parameters were measured: time and rate-pressure product at ischemia; intercept and slope of the linear regression between rate-pressure product and minutes of exercise. Group analysis showed that both drugs improved time to ischemia significantly and to the same extent. However, eight patients responded preferentially to verapamil in contrast to 12 patients on propranolol. The remaining four patients responded equally to both drugs. In verapamil responders, verapamil increased time to ischemia by decreasing intercept and increasing rate-pressure product at ischemia. In these patients, propranolol did not increase time to ischemia because of a marked decrease in rate-pressure product at ischemia. In propranolol responders the significant increase in time to ischemia during propranolol was the result of a decrease in intercept and slope. The ineffectiveness of verapamil in these patients was related to a slight decrease in intercept without any increase in rate-pressure product at ischemia. The preferential response to one of the two drugs could not be predicted on the basis of clinical and angiographic features. In conclusion, in patients with effort angina, medical treatment should be personalized and based on a direct and objective verification of a drug's efficacy since different mechanisms can modulate exercise tolerance.

Adult↗
PubMed1988

Septal thickness in human lungs assessed by computerized interactive morphometry.

We have studied the feasibility of using interactive computerized morphometric methods for the quantitation of septal thickness in the lung with the goal of introducing objective criteria for the diagnosis and grading of pulmonary fibrosis and edema. After reviewing available methods, we have decided in favor of linear intercept measurements of septal profiles which are limited to the tissue and therefore not affected by the level of lung inflation. Our method consisted in generating a graphic overlay of parallel lines over a real time video display of lung tissue. We had the options of measuring either uniformly oriented (random) or orthogonal intercepts. Randomly oriented intercepts (i.e., those with incidence angles ranging between 0 and 90 degrees) resulted in poor statistics because of excessive scattering of primary data; we resolved this difficulty by limiting the incident angle to the range of +/- 45 degrees from the normal to the septum at the point of sampling. This results in marked increase in consistency and reproducibility of the results with fewer measurements. Alternatively, we used intercepts measured over a line generated perpendicularly to the septal axis which approaches orthogonal thickness measurements. We found that both approaches yield acceptable results after as little as 50 measurements.

Computer Simulation↗
PubMed1981

Mathematical analysis of a phenytoin--disulfiram interaction.

A case of phenytoin-disulfiram drug interaction is analyzed with a mathematical technique used in enzyme kinetics. Serum anticonvulsant levels, obtained before, during, and after disulfiram administration, were collected from hospital records retrospectively. Phenytoin kinetic constants--maximal velocity of metabolism (Vmax) and Michaelis-Menten constant (km)--before, during, and after disulfiram administration, were compared. The slopes (km) of the regression lines analyzed by a small sample t test for parallelism were not significantly different (p greater than 0.05). Y-intercept (Vmax) values obtained before (433 mg/day) and after (463 mg/day) disulfiram are both significantly different when compared with the y-intercept during (264 mg/day) disulfiram administration, by a small-sample t test for common intercept (p less than 0.05). Changes in the elimination rate of phenytoin or changes in y-intercept result from noncompetitive drug effects. It is concluded that disulfiram affects phenytoin's elimination rate by noncompetitive mechanisms.

Disulfiram↗
PubMed1995

Methods for the quantification of DNA double-strand breaks determined from the distribution of DNA fragment sizes measured by pulsed-field gel electrophoresis.

Different methods were used for evaluating data for DNA double-strand breaks (DSBs), as obtained by pulsed-field gel electrophoresis (PFGE) after X irradiation of Chinese hamster ovary cells. A total of 60 data points in the dose range of 0 to 116 Gy, along with repair data for 30 and 60 Gy, were analyzed by four methods: (1) percentage of DNA released from the plug, (2) specific size markers (percentage of DNA less than specific sizes, (3) fragment size distributions and (4) shape of the molecular weight (M) distributions. With the last method, both the slope and the intercept of the logarithm of the amount of radioactive DNA/delta M/M plotted as a function of M were used for calculating DSBs/100 Mbp. The slope and the intercept analyses differ in that the former is relatively independent of DNA trapped in the agarose plugs, i.e. cannot be released by doses of 100-150 Gy, whereas the intercept is dependent on the percentage of DNA trapped. Also, calculations of DSBs/100 Mbp for methods 1, 2 and 3 depend on the amount of DNA trapped in the plug. However, the slope method is unreliable for doses below about 20 Gy, and the scatter of data points is much greater than that obtained by the intercept method and by methods 1, 2 and 3. Therefore, the fragment size distribution and the specific size marker methods give the most consistent results, with 0.49 +/- 0.03 (95% CI) (DSBs/100 Mbp)/Gy. With the specific size marker method, however, care must be taken in selection of size markers in relation to the levels of DSBs of interest. Assuming randomly distributed DSBs, all four methods gave essentially the same results; i.e., the dose response was linear with a calculated level of 0.5-0.6 (DSBs/100 Mbp)/Gy, which is the same as 0.47-0.62 determined previously by calibrating with 125IdU.

Animals↗
PubMed1993

Comparison of three data collection methodologies for the study of young illicit drug users.

Three data collection methods (street-intercept, telephone ring-in and focus-group discussions) were compared for their feasibility, reliability, validity and cost. The subjects of investigation were drug-related behaviours, attitudes and knowledge among current illicit drug users aged 16 to 21 years in Sydney. All three methods were found to be feasible and to produce reliable and valid information. Few differences in the demographic make-up and drug-use profiles of the samples were evident. The main differences between the data collections related to cost and the type of information obtained. The street-intercept method was the cheapest per completed interview and the focus-group method was the most expensive. Focus-group discussions were considered a valuable adjunct to the surveys because they facilitated an understanding of the quantitative survey results. It was concluded that the street-intercept method is the preferred survey method because of its lower cost and lower susceptibility to volunteer bias compared to the telephone ring-in. For repeated data collection to monitor changes in drug use patterns, street-intercept surveys in combination with focus-group discussions are recommended.

Adolescent↗
PubMed1993

Quality assurance of white blood cell labeling with a test based on adherence.

A new quality control assay was developed based on the premise that proper radioactive labeling should not affect the adherence characteristics of white blood cells to nylon fibers. Heparinized whole blood with trace amounts of radioactively labeled white blood cells was passed over nylon fiber columns and eluted in eight fractions. Percent radioactive adherence (%RA) and percent white blood cell adherence (%WBCA) were determined for each fraction. Regression lines (%RA versus %WBCA) were calculated for 9 samples labeled properly with 111In-oxine and for 17 samples intentionally subjected to improper labeling. Properly labeled preparations had a median slope = 1.05 and an intercept = 1%. Improperly labeled preparations had significantly lower slopes and/or higher intercepts. By the use of +/- 2 s.d. ranges as indicators of proper labeling (slope of 0.71-1.74; intercept of -35%-37%), the test had 100% sensitivity and 94% specificity. We conclude that proper labeling with 111In-oxine preserves the adherence characteristics of white blood cells, that improper labeling may affect the binding strength of white blood cells (decrease in slope) and/or lead to formation of sticky cell subgroups (increased intercept) and that the quality control assay can objectively assess the impact of labeling on adherence.

Cell Adhesion↗
PubMed1993

The effects of amrinone versus dobutamine on myocardial mechanics and energetics after hypothermic global ischemia.

The effects on the postischemic myocardium of amrinone and dobutamine were studied in canine hearts that underwent 90 minutes of hypothermic (10 degrees C) arrested ischemia. In an isolated heart preparation cross-circulated by a support dog, left ventricular pressure-volume loops were collected under a constant afterload based on a mock circulatory system and a range of preload conditions controlled by a computerized servo volume pump. Dobutamine (0, 5, 10, 15 micrograms/kg per minute) and amrinone (0, 0.75, 1.5, 3.0 mg/kg) were tested in this order based on the weights of the support dogs in eight experiments. Changes in intrinsic myocardial contractility were analyzed as percent increases in the preload recruitable stroke work area from baselines. Dobutamine exhibited significant dose-related increases in the preload recruitable stroke work area. Amrinone did not produce significant increases in preload recruitable stroke work area at 0.75 mg/kg; amrinone's inotropic effect was equivalent to dobutamine, 5 micrograms/kg per minute at 1.5 mg/kg, and at the maximum dose (3.0 mg/kg) it was equivalent to dobutamine, 10 micrograms/kg per minute. The myocardial energetic efficiency was determined from the analysis of the myocardial oxygen consumption-pressure volume area relationship. The y intercept represents the basal metabolic oxygen requirement of the unloaded beating heart, and the slope is inversely proportional to the rate of energy conversion for increasing loading conditions. Dobutamine significantly increased the y intercepts, but it had no effects on the slopes. These changes demonstrate reduced myocardial efficiencies that are consistent with previous reports. Amrinone (0.75 and 1.50 mg/kg) did not result in change of the y intercepts and the slopes of myocardial oxygen consumption-pressure-volume area relationship from baseline conditions. The y intercept was increased with amrinone (3.0 mg/kg), although still not significantly higher than baseline and not to the extents of the dobutamine group. Dobutamine did not have any primary effect on coronary resistance, while amrinone significantly reduced coronary resistance in all loading conditions at 1.5 and 3.0 mg/kg. This study demonstrates that the inotropic effects of amrinone tested under this constant afterload preparation were lower than those of dobutamine. Amrinone has a superior profile of myocardial efficiency on the postischemic myocardium since it does not produce the oxygen-wasting effects of the traditional inotropic agents such as the beta agonists. This benefit, together with amrinone's coronary dilating effects, critically improves the supply/demand ratio that may be of importance in certain clinical situations.

Amrinone↗
PubMed1996

Four frequently used test systems for serum cholesterol evaluated by isotope dilution gas chromatography-mass spectrometry candidate reference method.

We evaluated the performance of four frequently used cholesterol test systems, using split-sample measurements with a panel of 79 patients' specimens and isotope dilution gas chromatography-mass spectrometry (ID GS-MS) as a comparison method. The test systems were from Beckman, a Boehringer Mannheim, Merck, and Johnson & Johnson Clinical Diagnostics, performed on the Synchron CX7, Hitachi 717, Mega, and Ektachem 250 analyzers, respectively. The liner regression data for the method comparison [ID GS-MS as independent variable (x)] were for Beckman: slope = 1.012, intercept = 0.0243 mmol/L, dispersion (S(y/x)) = 0.1303 mmol/l, and correlation coefficient (r) = 0.9867; for Boehringer Mannheim: slope = 1.002, intercept = 0.114 mmol/L, Sy/x = 0.0759 mmol/L, r = 0.9954; for Merck: slope = 1.034, intercept = -0.0613 mmol/L, Sy/x = 0.0886 mmol/L, r = 0.9941; and for Johnson & Johnson Clinical Diagnostics: slope = 1.007, intercept = 0.01 mmol/L, Sy/x = 0.15 mmol/L, and r = 0.9811. These data demonstrate excellent state-of-the-art cholesterol measurement for some of the most widely used test systems.

Blood Chemical Analysis↗
PubMed1996

Glomerular basement membrane thickness - a comparison of two methods of measurement in patients with unexplained haematuria.

BACKGROUND: Thin glomerular basement membranes may be an important cause of microscopic haematuria. Unfortunately measurements are often not made because of the complicated methods currently employed. METHODS: A simplified method of measurement of glomerular basement membrane thickness, involving only 16 selected measurements on a single glomerulus, was compared with the accepted, but time-consuming, orthogonal intercept technique. Thirty-one needle biopsies from patients with renal haematuria unexplained by conventional histology and immunofluorescence were studied. Measurements were made on the same ultrathin sections. RESULTS: The new method was found to give much lower values (mean (SD) 202+/-51 versus 282+/-52 nm) with limits of agreement of -131 to -30 nm compared with the orthogonal intercept method. The coefficient of repeatability was 39 nm for the orthogonal intercept method and 56 nm for the new method. However, using two glomeruli the new method had limits of agreement of -120 to -41 nm with a coefficient of repeatability of 38 nm. CONCLUSIONS: Provided two glomeruli are measured the new technique is sufficiently accurate for the diagnosis of thin membrane nephrology, in appropriate cases, and is much simpler and cheaper than the orthogonal intercept method.

Adolescent↗
PubMed1996

Effect of photorefractive keratectomy on the accuracy of pneumatonometer readings in rabbits.

PURPOSE: To determine whether measurement of intraocular pressure (IOP) using a pneumatonometer is reliable after myopic 5 or 15 D excimer laser photoablation in rabbits. METHODS: Ten rabbits underwent 5 D myopic photorefractive keratectomy (PRK) of the left eye. Another seven rabbits underwent 15 D PRK: The right eye served as a control. The diameter of each PRK was 5 mm. Rabbits were examined 2.5 to 3 months later under general anesthesia. Eyes were cannulated, and the IOP was maintained at 5 to 40 mm Hg and measured using an intracameral manometer and a pneumatonometer at each pressure level; approximately 50 pressure points were formed. Readings of the two techniques were compared. RESULTS: Linear regression analysis comparing manometric and pneumatonometric readings revealed the following data in eyes with 5 D corrections (n = 10): correlation coefficient (r) = 0.926, slope = 1.058, and intercept = -3.133. The values of the unoperated control eyes were: r = 0.900, slope = 0.962, and intercept = -1.010. The following results were obtained in eyes with 15 D photoablation (n = 7): r = 0.876, slope 1.133, and intercept -3.147. Values for the control eye were: r = 0.885, slope = 1.175, and intercept = -3.497. When the manometer and pneumatonometer readings of all animals were compared, the adjusted squared correlation coefficient was 79%. When the variabilities associated with the animals and the PRK procedure (pooled 5 and 15 D corrections) were taken into account, adjusted squared correlation coefficient increased from 8% to 87%. CONCLUSIONS: Photorefractive keratectomy as high as 15 D/5 mm had only a minor effect on pneumatonometer readings in rabbits, indicating that the elastic properties of the cornea related to the accuracy of pneumatonometry were not significantly altered. Postoperative IOP monitoring with tonometers, based on flattening of the cornea under pressure, is accurate after PRK.

Animals↗
PubMed1995

Predictors of fixed orthodontic treatment in 15-year-old adolescents in South Australia.

An understanding of the determinants of the provision of fixed orthodontic treatment would be beneficial in the planning of any system aimed at rationalising supply. The aim of this longitudinal study was to determine those factors which were predictive of the provision of fixed orthodontic treatment in adolescents. Baseline data, at age 13 years, on oral health, the history of orthodontic consultation and interceptive orthodontic care, a dental appearance score (DAI), socio-demographic characteristics and self and parental perceptions of both dental appearance and need for fixed orthodontic treatment were obtained from 2793 adolescents under the care of the South Australian School Dental Service who had not undergone fixed orthodontic treatment. Data on the orthodontic care provided to these adolescents in the ensuing 2 years were collected. At the end of the 24-month period 433 adolescents (15.5%) had undergone fixed orthodontic treatment. Significant bivariate associations were found between the provision of fixed orthodontic treatment and the DAI score, sex of the adolescent, familial history of fixed orthodontic treatment, income, private insurance, orthodontic consultation and interceptive orthodontic care before the age of 13 years and self and parental perceptions of both dental appearance and the need for fixed orthodontic treatment. Logistic regression was used to produce a predictive model of fixed orthodontic treatment. The model explained 30.2% of the variance, with a specificity of 0.94, a sensitivity of 0.49 and a hit rate of 0.84%. Odds ratios greater than one were found for the DAI score, private insurance, females, self and parental perception of need, higher incomes and orthodontic consultation and interceptive orthodontic care before the age of 13 years.

Adolescent↗