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PubMed2003

Biomechanical superiority of plate fixation for proximal tibial osteotomy.

Proximal tibial osteotomies require secure and durable fixation to allow early range of motion; however, biomechanical data comparing commonly used fixation methods are lacking. The current study was done to quantify the dynamic biomechanical performance of blade staple fixation and plate fixation of simulated proximal tibial osteotomies. A 15 degrees proximal tibial osteotomy was done on each of 18 synthetic adult composite tibias. Blade staples were used as the means of fixation in nine tibias; plate fixation was used in the remaining nine tibias. The specimens were stressed cyclically in sinusoidal loading whose peak compression and tension loads imitate those measured during normal gait. Device performance was quantified by measuring displacement at the osteotomy site and the number of cycles to failure. Plate fixation had a greater fatigue life than staples (eight plates surviving past 200,000 cycles versus one blade staple) and showed a trend toward less displacement (0.69 mm versus 0.97 mm). Plate fixation of proximal tibial osteotomies offers better fixation and dynamic mechanical performance than blade staples.

Adult↗

PubMed2006

Quantitative analysis of changes in cervical intervertebral foramen size with vertebral translation.

STUDY DESIGN: Simulated translation of the C5 vertebra was performed in 20 embalmed cadaveric cervical spines, and cross-sectional areas of the C4-C5 and C5-C6 intervertebral foramina were measured and compared before and after translation of the C5 vertebra. OBJECTIVE: To determine the relationship of cross-sectional intervertebral foraminal areas to the degrees of vertebral translation. SUMMARY OF BACKGROUND DATA: The common feature of clinical instability and adjacent diseases of the cervical spine is malalignment of the cervical spine (i.e., there is ventral and dorsal translation of vertebral body with respect to the adjacent upper and lower vertebral body, respectively). To our knowledge, no previous study has analyzed the quantitative effect of vertebral translation on the size of the intervertebral foramina. METHODS: The cross-sectional areas of the intervertebral foramina at C4-C5 and C5-C6 were measured on computerized tomography. The images were then transferred to the personal computer, where consecutive dorsal translations of C5 vertebrae with a 1-mm increment from 1 to 5-mm displacements were performed using Microsoft paint software (Microsoft, Corp., Redmond, WA). National Institutes of Health (Bethesda, MD) Image J software (V1.33m) was then used to measure the areas of both sides of C4-C5 and C4-C6 foramina at normal and each displacement level in the computer. RESULTS: Following dorsal translation of C5 vertebra, anterolisthesis of C4 relative to C5 and retrolisthesis of C5 relative to C6 was noted. No significant difference was found between the measured values using Aquarius Image software (Microsoft, Corp.) on computerized tomography and National Institutes of Health image J software on the desktop computer (P > 0.05). When compared with normal values, there was an increase in the C4-C5 intervertebral foraminal area (i.e., 6%, 14%, 18%, 21%, and 26% with anterolisthesis of C4 relative to C5 following 1, 2, 3, 4, and 5-mm dorsal translation of the C5 vertebra, respectively). There was a 12% decrease in the C5-C6 intervertebral foraminal area, with each 1-mm incremental retrolisthesis of C5 relative to C6 vertebra. Statistically significant differences were found among residual cross-sectional foraminal areas following different degrees of dorsal translation (P < 0.05). CONCLUSION: There is a significant increase in size with anterolisthesis and decrease in size with retrolisthesis of upper and lower adjacent vertebral intervertebral foramina, respectively.

Aged↗

PubMed2006

A relook into the association of the estrogen receptor [alpha] gene (PvuII, XbaI) and adolescent idiopathic scoliosis: a study of 540 Chinese cases.

STUDY DESIGN: A genetic association study of estrogen receptor-[alpha] gene (ESR1) with adolescent idiopathic scoliosis (AIS) in Chinese. OBJECTIVES: To investigate whether: 1) PvuII and XbaI polymorphisms in ESR1 are predisposition factor for AIS and 2) these polymorphisms correlate with the severity of curvature in AIS. SUMMARY OF BACKGROUND DATA: A common single nucleotide polymorphism (SNP) in ESR1 (XbaI) was found to be associated with curve severity in Japanese AIS patients recently. The role of ESR1 as a predisposition gene using a case-control design in other ethnic groups is required to confirm the previous associations. METHODS: A total of 540 Chinese AIS girls with Cobb angle above 20 degrees were recruited as cases together with 260 healthy controls. The effect of ESR1 SNPs on severity of scoliosis was analyzed in a subgroup of AIS patients (n = 364) followed up until skeletal maturity with the maximum Cobb angle recorded. Two SNPs in ESR1 were genotyped by PCR-restriction fragment length polymorphism in all subjects. RESULTS: The allelic frequency of X allele was 23% in both case and control groups. The P allele was found at allelic frequency of 40% and 36% in the case and control groups, respectively. No association between the two ESR1 SNPs and the occurrence of AIS by both genotype and haplotype analysis could be established, suggesting that both SNPs were not predisposition alleles for AIS. AIS patients with different genotypes showed no difference in the maximum Cobb angle. No association was found between the genotype and anthropometric measurements in AIS patients. CONCLUSION: The previously reported association with curve severity could not be replicated in our large series of Chinese AIS patients. The current study also did not show any association of the 2 SNPs with increased risk of having AIS.

Adolescent↗

PubMed1985

Extinction coefficients of chlorophyll a and B in n,n-dimethylformamide and 80% acetone.

We found inconsistencies in the commonly used data for chlorophyll analysis in 80% acetone. Recently developed extinction coefficients for chlorophyll b in N,N-dimethylformamide (DMF) based on values from 80% acetone are low as a result of these inconsistencies. We determined extinction coefficients of chlorophyll a (Chl a) and chlorophyll b (Chl b) in DMF for wavelengths of 618 to 665 nanometers. The simultaneous equations necessary for quantifying Chl a, Chl b, or total Chl in DMF in the absence of other chlorophyllous pigments are: Chl a = 12.70A(664.5) - 2.79A(647); Chl b = 20.70 A(647) - 4.62A(664.5); total Chl = 17.90A(647) + 8.08A(664.5), where A = absorbance in 1.00 centimeter cuvettes and Chl = milligrams per liter.N,N-Dimethylformamide is a very convenient solvent for Chl extraction since it is effective on intact plant parts and Chl is quite stable in DMF. There was no difference in the amount of Chl extracted when plant tissue was stored for 1 or 3 days at three temperatures, with or without solvent added.

Journal Article↗

PubMed1999

In vivo hemodynamic evaluation based on transverse Doppler measurements of blood velocities and vessel diameter.

We have developed a method for simultaneously measuring the blood flow velocity distributions along a line perpendicular to the vessel wall and the instantaneous diameter of the common carotid artery. Thus, the wall shear rates and shear rate distribution across the arterial lumen could be computed accurately. In this method, transverse Doppler technique is combined with ultrasonic A echo-mode, using only one single crystal transducer. In order to satisfy the requirements of high spatial and velocity resolutions, especially extending to a very low velocity range in the case of low signal-to-noise ratio, a combination scheme of 10-MHz operating frequency, sample volume tracking, 12-bit A/D, 512-point fast Fourier transform with 5-kHz sample rate, spectrum average, variable threshold for bandwidth estimation, smoothing of velocity curves, and hardware was carefully designed. The velocity distribution measurements based on transverse Doppler spectrums were also validated under the steady flow conditions using a flow loop system. Results from this study show this ultrasonic system to be capable of measuring the shear rates at wall accurately and shear rate distributions across the common carotid arterial lumen.

Adult↗

PubMed2005

Face detection using spectral histograms and SVMs.

We present a face detection method using spectral histograms and support vector machines (SVMs). Each image window is represented by its spectral histogram, which is a feature vector consisting of histograms of filtered images. Using statistical sampling, we show systematically the representation groups face images together; in comparison, commonly used representations often do not exhibit this necessary and desirable property. By using an SVM trained on a set of 4500 face and 8000 nonface images, we obtain a robust classifying function for face and non-face patterns. With an effective illumination-correction algorithm, our system reliably discriminates face and nonface patterns in images under different kinds of conditions. Our method on two commonly used data sets give the best performance among recent face-detection ones. We attribute the high performance to the desirable properties of the spectral histogram representation and good generalization of SVMs. Several further improvements in computation time and in performance are discussed.

Algorithms↗

PubMed2003

The contribution of insurance coverage and community resources to reducing racial/ethnic disparities in access to care.

OBJECTIVE: To examine the extent to which health insurance coverage and available safety net resources reduced racial and ethnic disparities in access to care. DATA SOURCES: Nationally representative sample of 11,692 African American, 10,325 Hispanic, and 74,397 white persons. Nonelderly persons with public or private health insurance and those who were uninsured. STUDY DESIGN: Two cross-sectional surveys of households conducted during 1996-1997 and 1998-1999. DATA COLLECTION: Commonly used measures of access to and utilization of medical care were constructed for individuals. These measures include the following. (1) percent reporting unmet medical needs, (2) percent without a regular health care provider, and (3) no visit with a physician in the past year. FINDINGS: More than 6.5 percent of Hispanic and African Americans reported having unmet medical needs compared to less than 5.6 percent of white Americans. Hispanics were least likely to see the same doctor at their usual source of care (59 percent), compared to African Americans (66 percent) and whites (75 percent). Similarly, Hispanics were less likely than either African Americans or whites to have seen a doctor in the last year (65 percent compared to 76 percent or 79 percent). For Hispanics, more than 80 percent of the difference from whites was due to differences in measured characteristics (e.g., insurance coverage, income, and available safety net services). Differences in measured characteristics between African Americans and whites explained less than 80 percent of the access disparities. CONCLUSION: Lack of health insurance was the single most important factor in white-Hispanic differences for all three measures and for two of the white-African American differences. Income differences were the second most important factor, with one exception. Community characteristics generally were much less important, with one exception. The positive effects of insurance coverage in reducing disparities outweigh benefits of increasing physician charity care or access to emergency rooms.

Adult↗

PubMed2000

Wildlife population assessment: past developments and future directions.

We review the major developments in wildlife population assessment in the past century. Three major areas are considered: mark-recapture, distance sampling, and harvest models. We speculate on how these fields will develop in the next century. Topics for which we expect to see methodological advances include integration of modeling with Geographic Information Systems, automated survey design algorithms, advances in model-based inference from sample survey data, a common inferential framework for wildlife population assessment methods, improved methods for estimating population trends, the embedding of biological process models into inference, substantially improved models for conservation management, advanced spatiotemporal models of ecosystems, and greater emphasis on incorporating model selection uncertainty into inference. We discuss the kind of developments that might be anticipated in these topics.

Algorithms↗

PubMed2003

Bayesian modeling of age-specific survival in bird nesting studies under irregular visits.

In this article, a Bayesian model for age-specific nest survival rates is presented to handle the irregular visit case. Both informative priors and noninformative priors are investigated. The reference prior under this model is derived, and, therefore, the hyperparameter specification problem is solved to some extent. The Bayesian method provides a more accurate estimate of the total survival rate than the standard Mayfield method, if the age-specific hazard rates are not constant. The Bayesian method also lets the biologist look for high- and low-survival rates during the whole nesting period. In practice, it is common for data of several types to be collected in a single study. That is, some nests may be aged, others are not. Some nests are visited regularly; others are visited irregularly. The Bayesian method accommodates any mix of these sampling techniques by assuming that the aging and visiting activities have no effect on the survival rate. The methods are illustrated by an analysis of the Missouri northern bobwhite data set.

Aging↗

PubMedDate not supplied

Inhibition of acetylcholinesterase by histamine agonists and antagonists.

The histamine H1 and/or H2-receptor agonists showed weak acetylcholinesterase inhibitory activity. Their dissociation constants (Kis and/or Kii) were 2-methyl histamine (Kis = 1751 mumol/l, s.e. = 163) less than 4-methyl histamine (Kis = 3551 mumol/l, s.e. = 414) less than dimaprit (Kis = 2931 mumol/l, s.e. = 605; Kii = 3668 mumol/l, s.e. = 901) less than histamine (Kis = 6480 mumol/l, s.e. = 1360). Both histamine H1 and H2-receptor antagonists showed stronger acetylcholinesterase inhibitory activity. Their dissociation constants were ranitidine (Kii = 1.56 mumol/l, s.e. = 0.14) less than oxmetidine (Kis = 14.7 mumol/l, s.e. = 1) less than mepyramine (Kis = 178 mumol/l, s.e. = 23; Kii = 440 mumol/l, s.e. = 98) less than cimetidine (Kis = 199 mumol/l, s.e. = 12; Kii = 827 mumol/l, s.e. = 126). Using the ROSFIT programs for fitting data to common enzyme kinetic models, the inhibition caused by histamine, 4-methyl histamine, 2-methyl histamine, oxmetidine and neostigmine was of the competitive type. Mepyramine, cimetidine and dimaprit appeared to exhibit the modern non-competitive type of inhibition with their primary action on the enzyme rather than on the enzyme-substrate complex. Ranitidine seemed to act on the enzyme-substrate complex rather than the enzyme, conforming to the uncompetitive inhibition model. The clinical implications of acetylcholinesterase inhibition by cimetidine and ranitidine are discussed.

Acetylcholinesterase↗

PubMed2005

Moderately thermophilic Myxobacteria: novel potential for the production of natural products isolation and characterization.

Novel moderately thermophilic Myxobacteria from both known suborders (Cystobacterineae and Sorangineae) were isolated from soil samples of semiarid and warm climates. The addition of the anthelmintic and amoebizidal agent levamisole was a new and crucial improvement for the fast isolation of overall 37 strains, which grew very fast at temperatures of 42-44 degrees C. When the 16S rDNAs were compared with GenBank data of common Myxobacteria, identities were 98-99%, thus not reflecting the physiological differences. Similar to the Myxobacteria described so far, the new isolates are multiresistant against a variety of antibiotics and are producers of typical myxobacterial secondary metabolites. Analysis of our previous strain collection isolated from soil samples taken worldwide revealed a more or less uniform distribution of strains which synthesize specific metabolites. Therefore these moderately thermophilic Myxobacteria, which grow 2-3 times faster, have the potential to replace the slow-growing isolates and provide a means for fast and cost-saving production of myxobacterial metabolites in the future.

Biological Products↗

PubMed2004

Chronic daily headaches in children and adolescents: a study of clinical characteristics.

The clinical characteristics of chronic daily headache were studied in 40 children and adolescents, as well as the associated factors responsible for maintenance of the continuous headache pattern. The study of the clinical headache characteristics, showed a female preponderance (75%), mean age of 11 years old at the first consultation, and onset of headache symptomatology at a mean age of 8.5 years old. The average time interval for the evolution of sporadic headache into chronic daily headache was 1.4 years, and psychosocial stressors were present, acutely or chronically, during the period of headache-frequency increase in 47% of the children. Headaches were classified as transformed migraine (65%), mixed pattern (17.5%) and chronic tension-type headache (17.5%). Sixty per cent of patients had mothers with migraine. Data regarding common analgesic use showed an average intake of 11.2 days/month.

Adolescent↗

PubMed1984

The blood-brain barrier lesion and the systemic convulsant model of epilepsy.

Systemic kainic acid (KA) at 1 mg/kg crosses the normal blood-brain barrier (BBB) of rats to produce scattered sharp waves for approximately 10 min on the EEG, but is without observable effect, producing no EEG or behavioral changes, at 0.5 mg/kg. When the BBB is opened in most of one hemisphere by 6,000 rads, the rats are clinically normal and have a normal EEG. When the irradiated rats are challenged with 0.5 mg/kg KA, intense, highly lateralized epileptiform bursts result; these bursts last 1-10 s and recur for 90 mins. This phenomenon is repeatable for the 1 week that the BBB is open. The results are identical when the BBB is opened with a pin lesion. Because endogenous glutamate agonists are common, these data suggest a possible pathophysiologic mechanism for human epilepsy.

Animals↗

PubMed1997

Circadian rest-activity rhythms in demented and nondemented older community residents and their caregivers.

OBJECTIVE: Disruptive nocturnal behaviors (DNBs) of older people often threaten the caregiving arrangements on which their community tenure depends. Dementing disorders are especially prone to result in disrupted sleep and agitated behaviors ("sundowning"). The objective here was to develop an objective correlate of DNBs, by which their severity and effects on caregivers can be measured. DESIGN: Quantitative comparison of subjective sleep and motor activity patterns in older people and their caregivers. It was hypothesized that older people with reported DNBs would be more motorically active at night than their caregivers. SETTING: Subjects' homes. PARTICIPANTS: Twenty-five demented and 18 nondemented older day-care participants and their paired caregivers. MEASUREMENTS: Older subjects and caregivers simultaneously kept daily sleep logs and recorded wrist motor activity every .5 minute for 9 days. A novel method was devised to identify and exclude from analysis periods when the activity monitor was not being worn. Such periods were common. Activity data were analyzed by computing hourly means and by fitting cosine models by least squares. RESULTS: Demented older people were not significantly more active at night than their caregivers, though group differences varied by time of night. They were significantly less active in the daytime than were their caregivers. Nondemented older people were significantly more active at night than their caregivers and were as active by day as their caregivers. The caregivers of demented and nondemented older people had similar rest-activity patterns. The mean amplitudes of cosine models were smaller in the older adults. Acrophases (peaks) fell between 2 and 3 pm and did not differ significantly among the groups. CONCLUSIONS: As a result of increased nighttime motor activity and decreased daytime activity, rest-activity rhythms were flatter in older adults than in caregivers. This was not explained fully by age and does not necessarily imply that the output of a circadian pacemaker was low. Decreased daytime activity may have resulted from deficient physical stimulation or frailty. Frailty may also explain why nighttime activity was not more elevated in the demented older people. Increased nighttime activity is probably explained by depression, sleep-schedule disturbances, restless legs, or other sleep disorders. Judging by their shared variations of activity, caregivers interacted mainly with the demented older people at bedtime and at rising time in the morning.

Aged↗

PubMed1988

Symptomatic sinus node dysfunction after heart transplantation.

When donor hearts are studied systematically after transplantation, by programmed electrical stimulation, sinus node dysfunction has been found to be common though data regarding symptoms related to this phenomenon are not available. In this case report we describe a heart transplant recipient who experienced serious symptomatic sinus node dysfunction associated with transient atrial fibrillation 17 days after cardiac transplantation; there was no evidence of donor heart rejection. Intracardiac electrophysiology testing confirmed sinus node dysfunction of the donor heart, but only with relatively rapid atrial pacing rates.

Adult↗

PubMed2005

Partly conditional survival models for longitudinal data.

It is common in longitudinal studies to collect information on the time until a key clinical event, such as death, and to measure markers of patient health at multiple follow-up times. One approach to the joint analysis of survival and repeated measures data adopts a time-varying covariate regression model for the event time hazard. Using this standard approach, the instantaneous risk of death at time t is specified as a possibly semi-parametric function of covariate information that has accrued through time t. In this manuscript, we decouple the time scale for modeling the hazard from the time scale for accrual of available longitudinal covariate information. Specifically, we propose a class of models that condition on the covariate information through time s and then specifies the conditional hazard for times t, where t > s. Our approach parallels the "partly conditional" models proposed by Pepe and Couper (1997, Journal of the American Statistical Association 92, 991-998) for pure repeated measures applications. Estimation is based on the use of estimating equations applied to clusters of data formed through the creation of derived survival times that measure the time from measurement of covariates to the end of follow-up. Patient follow-up may be terminated either by the occurrence of the event or by censoring. The proposed methods allow a flexible characterization of the association between a longitudinal covariate process and a survival time, and facilitate the direct prediction of survival probabilities in the time-varying covariate setting.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Age changes in bone.

Changes in bone structure as a function of age have been studied by simple inspection, x-ray imaging, stereo-photography, deep field optical microscopy, circularly polarised light microscopy, and scanning electron microscopy (SEM), including both topographic and compositional backscattered electron (BSE) imaging modes. The study of bone as a three-dimensional object, rather than in thin sections, enables us to envisage modelling and remodelling processes in context. The study of ultra-flat block surfaces permits the acquisition of data from an effectively very thin layer in the block face, and to examine bone as a spectrum of tissue types varying in the degree of mineralisation. Particular attention has been paid in our earlier studies to the iliac crest, lumbar vertebral bodies, femoral mid-shaft, neck and head and parietal and frontal skull bones. Recently, we have compared findings from these sites with observations on the mandible. We conclude, from our new imaging data, that common generalisations about the changes in bone in ageing and osteoporosis are too simplified, and that the mandible differs sufficiently from post-cranial skeletal sites that it would be unwise to extrapolate from findings in the jaw to the circumstances elsewhere.

Age Factors↗

PubMedDate not supplied

Modeling multiscale heterogeneity and aquifer interconnectivity.

A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer. The region is conceptualized as having a hierarchical organization with three facies assemblage types (large-scale heterogeneity) and two facies types within each assemblage (small-scale heterogeneity). We statistically characterized the sedimentary architecture at both scales, formulated indicator correlation models from those characterizations, and used the models to simulate the architecture in a multiscale realization. We focused on the interconnectivity of units creating higher-permeability pathways. Higher-permeability pathways span the realization even though the proportion of higher-permeability facies is less than the percolation threshold. Thus, geologic structures as represented in the indicator correlation models create interconnectivity above that which would occur if the higher-permeability facies were randomly placed. This amount of interconnection among higher-permeability facies within the multiscale realization is consistent with that suggested in prior hydraulic and geochemical studies of the regional system.

Geologic Sediments↗