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PubMed2004

Increase of the apnoea-hypopnoea index after uvulopalatopharyngoplasty: analysis of failure.

From 70 patients who had uvulopalatopharyngoplasty (UPPP) operation and a pre- and postoperative sleep registration, we could retrospectively determine the failures and the correlation between variables such as age, gender, body mass index (BMI), earlier or concomitant tonsillectomy, unilevel (uvula-palate-tonsil) or multilevel (base of tongue as well) obstruction during sleep endoscopy and treatment outcome. From 70 patients, the preoperative sleep registration classified 15 social unacceptable snorers and 55 obstructive sleep apnoea syndrome (OSAS) patients. In this study we focused on the OSAS patients. From the 55 OSAS patients, 32 were classified as successful after UPPP, because they had a decreased apnoea-hypopnoea index (AHI) after surgery (</=20). Eight patients had a decreased AHI, but more than 20 apnoeas/hypnoeas per hour. Fifteen patients were identified as UPPP failures with an equal or increased AHI and/or subjective deterioration of snoring. We were unable to find a statistically difference between the two groups with respect to variables such as age, BMI and AHI preoperative (P > 0.56) as between the level of obstruction(s) (P > 0.24). For earlier or concomitant tonsillectomy we found a statistically difference (P > 0.039), but a very small number in the high failure group (n = 8). We conclude that although sleep endoscopy adds to better patient selection and better results, paradoxically, the finding of obstruction on palate-uvula level during sleep endoscopy can still give UPPP failures.

Adult↗
PubMed1994

Knowledge discovery of multilevel protein motifs.

A new category of protein motif is introduced. This type of motif captures, in addition to global structure, the nested structure of its component parts. A dataset of four proteins is represented using this scheme. A structured machine discovery procedure is used to discover recurrent amino acid motifs and this knowledge is utilized for the expression of subsequent protein motif discoveries. Examples of discovered multilevel motifs are presented.

Animals↗
PubMed1999

The Helicobacter pylori genome: from sequence analysis to structural and functional predictions.

Fold assignments for proteins from the Helicobacter pylori genome are carried out using BASIC, a profile-profile alignment algorithm recently tested on the Mycoplasma genitalium and Escherichia coli genomes. The fold assignments are followed by automated function evaluation, based on the multilevel description of functional sites in proteins. Over 40% of the proteins encoded in the H. pylori genome can be recognized as belonging to a protein family with known structure. Previous estimates suggested that only 10-15% of genome proteins could be characterized this way. This dramatic increase in the number of recognized homologies between H. pylori proteins and structurally characterized protein families is partly due to the rapid increase of the database of known protein structures, but mostly it is due to the significant improvement in prediction algorithms. Knowledge of a protein fold adds a new dimension to our understanding of its function and, similarly, structure prediction can also add to understanding, verification, and/or prediction of function for uncharacterized proteins. Several examples analyzed in more detail in this article illustrate insights that can be achieved from structure and detailed function prediction.

Algorithms↗
PubMed2002

Improving medication compliance of a patient with schizophrenia through collaborative behavioral therapy.

Introduction by the column editors: Numerous factors influence a patient's decision to accept or reject prescribed medications, including the patient's personal values, environmental conditions, and the quality of the patient-physician relationship (1). Guidelines for evaluating and managing noncompliance with medication regimens by patients with schizophrenia take this multidimensional perspective into account, emphasizing functional assessment of nonadherence behaviors and individualized behavior-change strategies to secure and maintain the patient's cooperation (2). Moreover, a collaborative approach to planning pharmacotherapy is required to ensure medication compliance, with a particular emphasis on linking the positive effects of medications with the patient's personal goals and desires for better functioning and quality of life (3). The following case study illustrates the application of principles for enhancing medication compliance in the treatment of a woman diagnosed as having schizophrenia, paranoid type. Strategies presented by Dr. Heinssen include collaborative treatment contracts, analysis of adherence behaviors, and techniques for boosting medication cues and reinforcers in the patient's home. The therapy described was provided in the Life Skills partial hospitalization and psychiatric rehabilitation program, a multidisciplinary, multilevel outpatient service of the now-closed Chestnut Lodge Hospital in Rockville, Maryland. The program integrated medical, social-learning, and cognitive-behavioral interventions for psychosis within a psychiatric rehabilitation framework.

Cognitive Behavioral Therapy↗
PubMedDate not supplied

[Correlation of biophysical parameters of biologically active points and variations of heliogeophysical factors].

The correlation between the parameters of biologically active points and the dynamics of solar activity was studied. Statistically significant correlations between electroconductivity of biologically active points and solar activity indices (sunspot number, Ap-index, solar radiowave flux) were revealed. The spectral analysis of the temporal organization of biologically active points revealed a set of periods present in the dynamics of solar activity. It was concluded that bioelectric system of the human organism is a complicated multilevel time-structure, which effectively reacts to changes in heliogeophysical dynamics. The bioelectric system of biologically active points is considered to be one of general information channels of electromagnetic nature, which realize the connection of organism with environment.

Acupuncture Points↗
PubMed1982

Simultaneous electron capture detection of chlorpyrifos and 3, 5, 6-trichloro-2-pyridinol residues in peach and bahia grass field samples following gel permeation cleanup.

A recently published method involving the simultaneous extraction, gel permeation cleanup, and electron capture gas chromatographic detection of residues of the insecticide and acaricide chlorpyrifos and its principal metabolite 3,5,6-trichloro-2-pyridinol is successfully applied to Lorsban-treated peach and Bahia samples. Previous quantitation of these compounds has required 2 separate analytical procedures. Multilevel temperature programming and manipulation of the gel permeation column effluent rate are the only adjustments of experimental parameters necessary to avoid large amounts of gas chromatographic interferences. Chromatographic peaks are more clearly defined and easier to integrate with the multilevel program than they are with 2-step or linear programs. This is one reason that recovery data are improved over those reported for the method as applied in the pea vine work. Residue analysis conducted on field-treated peaches and Bahia grass show the newly published procedure to be sensitive and effective.

Chlorpyrifos↗
PubMed1995

Surface analysis in microelectronics.

The contribution given by surface analysis to solve some problems encountered in the production of electronic power devices have been discussed. Mainly two types of problems have been faced. One of these deal with interfacial chemistry. Three examples have been investigated. The first applies to the improvement of the quality and the reliability of plastic packages through the optimization of the resin/metal and resin/die adhesion. The second relies to the adhesion between polyimide and silicon nitride used in the multilevel technology. The third example refers to the so called die-attach process and related problems. Another area of interest in microelectronics is that of the erosion of various types of surfaces and the possibility of wrong etching. A few examples of the application of surface analytical techniques for these problems will be presented. XPS and SIMS working in imaging and multipoint analysis mode, scanning acoustic microscopy, contact angle measurements as well as peeling and tensile strength measurements are the main tools used to obtain useful data.

Journal Article↗
PubMed2003

Detection and segmentation of drusen deposits on human retina: potential in the diagnosis of age-related macular degeneration.

Assessment of the risk for the development of age-related macular degeneration requires reliable detection and quantitative mapping of retinal abnormalities that are considered as precursors of the disease. Typical signs for the latter are the so-called drusen that appear as abnormal white-yellow deposits on the retina. Segmentation of these features using conventional image analysis methods is quite complicated mainly due to the non-uniform illumination and the variability of the pigmentation of the background tissue. This paper presents a novel segmentation algorithm for the automatic detection and mapping of drusen in retina images acquired with the aid of a digital Fundus camera. We employ a modified adaptive histogram equalization, namely the multilevel histogram equalization (MLE) scheme, for enhancing local intensity structures. For the detection of drusen in retina images, we develop a novel segmentation technique, the histogram-based adaptive local thresholding (HALT), which extracts the useful information from an image without being affected by the presence of other structures. We provide experimental results from the application of our technique to real images, where certain abnormalities (drusen) have slightly different characteristics from the background. The performance of the algorithm is established through statistical analysis of the results. This analysis indicates that the proposed drusen detector gives reliable detection accuracy in both position and mass size.

Algorithms↗
PubMed2004

Efficacy of osteogenic protein-1 in a challenging multilevel fusion model.

STUDY DESIGN: A therapeutic study compared the influence of osteogenic protein-1 to autograft and collagen carrier in multilevel sheep spine fusions. OBJECTIVE: To evaluate the efficacy of osteogenic protein-1 compared to autograft and collagen carrier in achieving fusion in a challenging multilevel lumbar spine ovine model. SUMMARY OF BACKGROUND DATA: Bone morphogenetic proteins can successfully augment spinal fusion. To date, all the preclinical and clinical studies using bone morphogenetic proteins have evaluated single-level fusion. In practice, multiple level fusions are commonly required for various conditions, like spinal deformity. METHODS: Eighteen sheep underwent three-level spine fusion. Six sheep were treated with osteogenic protein-1 and its carrier, autograft, or with the carrier alone. Specimens were analyzed for evidence of fusion by palpation, radiographic and histologic analysis, and biomechanical testing. RESULTS: Manual palpation testing for the presence of fusion showed none of the specimens fused all three levels or fused at the lumbosacral junction. No statistically significant difference was found between the osteogenic protein-1 and autograft groups' fusion rates based on radiographic grading (P = 0.65) or biomechanical testing. Histologic analysis showed no qualitative difference in bone morphology or cellularity of fusion masses when comparing the autograft and osteogenic protein-1 specimens. CONCLUSIONS: No model before this exists that tests the efficacy of bone morphogenic proteins in as challenging an environment. Extrapolation of single-level preclinical and clinical studies with bone morphogenic proteins for use in multilevel fusion requires careful review. Autograft and osteogenic protein-1 had similar rates of fusion. A high rate of nonunion is seen with this multiple level fusion to the sacrum using autograft or osteogenic protein-1. The biologic enhancement with osteogenic protein-1 is not able to overcome this mechanically rigorous model.

Animals↗
PubMed2000

Serial fetal lung volume measurement using three-dimensional ultrasound.

OBJECTIVE: To establish reference intervals for fetal lung growth. DESIGN: Longitudinal observational study. SUBJECTS: Fifty-eight women with initially uncomplicated singleton pregnancies were recruited from the antenatal population of a teaching hospital. Four women were excluded from the final analysis because of complications arising in their pregnancy. METHODS: Each subject was serially scanned at monthly intervals. At each visit lung volume was measured using an ultrasound-based computerized three-dimensional imaging system. Multilevel models were used to determine conditional and unconditional reference intervals. RESULTS: Reference intervals for fetal lung growth were derived. Fetal lung volume increases in a non-linear way with gestation. CONCLUSIONS: Our computerized system has the capacity to be used in conjunction with any standard two-dimensional ultrasound scanner in order to measure volume. Lung volume measurement may be useful in predicting pulmonary hypoplasia.

Adult↗
PubMedDate not supplied

The peer group as a context for the development of young adolescent motivation and achievement.

This study investigated the peer group as a context for the socialization of young adolescents' motivation and achievement in school. Social network analysis was used to identify peer groups of adolescents in middle school whose members regularly interacted with each other (N = 331). Actual reports from these peer group members were used to assess peer group characteristics. Multilevel analyses indicated that peer groups did socialize some academic characteristics, controlling for selection factors. Students' peer group context in the fall predicted changes in their liking and enjoyment of school (intrinsic value) and their achievement over the school year. Students' peer group context was unrelated to changes in their beliefs about the importance of school (utility value) or expectancies for success over the school year.

Adolescent↗
PubMed2004

Radiographic parameters as prognostic indicators for healing of class II furcation defects.

OBJECTIVE: To evaluate radiographic measurements for use as prognostic indicators for healing of class II furcation defects following regenerative therapy. MATERIAL AND METHODS: In 17 patients (eight females), 33 class II furcation defects (mandibular buccal (n=10) and lingual (n=12), and maxillary buccal (n=11)) were treated using the barrier membrane technique. Twenty-six furcations were treated using a bioabsorbable membrane, while a nonresorbable membrane was used to treat the remaining seven furcation defects. Clinical parameters and standardized radiographs were obtained before as well as 6 and 24 months after therapy. All radiographs were digitized and evaluated by an examiner blinded to the clinical data. The following distances were measured: cemento-enamel junction line (CEJ-line) to alveolar crest (AC) at the furcation site (AC-CEJ line), CEJ-line to the furcation fornix (Fx-CEJ line), width of the furcation at the level of the AC (FW) as well as the distance from Fx to a straight line between the AC mesial and distal of the tooth (Fx-AC line). RESULTS: Statistically significant (p<0.001) horizontal attachment gains could be observed 6 and 24 months after therapy (6 months: 1.49+/-0.85 mm; 24 months: 1.14+/-0.91 mm). However, a small but statistically significant (p=0.031) attachment loss of 0.35 mm was observed between the 6 and 24 months examination. Multilevel regression analyses identified baseline probing depth (p=0.0017) and 3 of the radiographic distances as prognostic factors: Fx-CEJ line (p=0.014), FW (p=0.0535), Fx-AC line (p=0.0827). CONCLUSION: The analysis of presurgical radiographs may yield information on the success of the regenerative therapy of buccal and lingual class II furcation defects. A long root trunk, a wide furcation entrance and an Fx coronal to the AC have negative influences on the success of therapy. Further, a deep probing depth at the furcation site at baseline increases the likelihood for more favourable horizontal attachment gain in furcations.

Absorbable Implants↗
PubMed2004

An analysis of an older driver evaluation program.

OBJECTIVES: To identify elements of an older driver evaluation program that predict driving performance in older adults. SETTING: Outpatient medical clinic in an academic medical center. DESIGN: A retrospective analysis. PARTICIPANTS: Six hundred sixty-four older adults who were referred to an older driver evaluation program. MEASUREMENTS: A physician trained in geriatric medicine and a clinical geriatric nurse specialist oversaw an experienced driving evaluator and an occupational therapist who conducted assessments of older persons' functional status; reaction time; driving skills; and cognitive, hearing, and vision abilities. Self-report data along with a medical history submitted by patients' primary care physicians supplemented the clinical assessments. RESULTS: A multinomial logistic regression revealed that the Mini-Mental State Examination (MMSE), cues needed with the Trail Making Test, Part B, grip strength, and an interaction effect between the MMSE and reaction time constituted the most parsimonious model for predicting on-the-road performance. A receiver operating characteristic analysis indicated that this index had good sensitivity but low specificity. A binomial regression comparing imperfect and perfect drivers demonstrated the significance of the Traffic Sign and Visual Perception tests. CONCLUSION: Clinicians should employ a multilevel screening process that includes initial cognitive tests, such as the MMSE and the Trail Making Test, Part B, although more studies of driving evaluation programs in medical settings that include random samples of older drivers are needed.

Aged↗
PubMed2006

MRI of clot in cerebral venous thrombosis: high diagnostic value of susceptibility-weighted images.

BACKGROUND AND PURPOSE: In cerebral venous thrombosis (CVT), the sensitivity of conventional MRI sequences to detect clot in the sinuses or veins is incomplete and largely depends on the time elapsed since thrombus formation. Little is known concerning the corresponding diagnostic value of fluid-attenuated inversion recovery (FLAIR), echo-planar T2* susceptibility-weighted imaging (T2*SW) or diffusion-weighted images (DWI). METHODS: We performed a retrospective analysis of 114 MRI examinations from 39 patients with CVT using a structured assessment. The time course of sensitivity in the detection of clot (n=166 clots) was analyzed for different MR sequences using a multilevel logistic model. The sensitivity of different MR sequences for diagnosis of cortical venous thrombosis was tested separately (n=38 clots). RESULTS: The sensitivity of T2*SW and T1-weighted spin echo image (T1SE) sequences to detect clot in the sinuses or veins was estimated at 90% and 71% between day 1 and day 3, which was much higher than that of T2SE, FLAIR or DWI during the first week of clinical onset. The sensitivity of T2*SW was stable in the first week. After this period, the sensitivity of T2*SW decreased less than that of T1SE. Thrombosed cortical veins, even in the absence of visible occlusion on magnetic resonance venography, were detected more frequently with T2*SW (97%) and T1SE (78%) than with FLAIR or DWI (<40%). CONCLUSIONS: T2*SW imaging appears to be of additional diagnostic value in CVT. The T2*SW sequence may be particularly useful during the acute phase of CVT when the sensitivity of the other sequences is incomplete and for the diagnosis of isolated cortical venous thrombosis.

Adolescent↗
PubMed2003

Assessing psychological change in adulthood: an overview of methodological issues.

This article reviews the current status of methods available for the analysis of psychological change in adulthood and aging. Enormous progress has been made in designing statistical models that can capture key aspects of intraindividual change, as reflected in techniques such as latent growth curve models and multilevel (random-effects) models. However, the rapid evolution of statistical innovations may have obscured the critical importance of addressing rival explanations for statistical outcomes, such as cohort differences or practice effects that could influence estimates of age-related change. Choice of modeling technique and implementation of a specific modeling approach should be grounded in and reflect both the theoretical nature of the developmental phenomenon and the features of the sampling design that selected persons, variables, and contexts for empirical observation.

Adult↗
PubMed2006

Conceptualizing and testing random indirect effects and moderated mediation in multilevel models: new procedures and recommendations.

The authors propose new procedures for evaluating direct, indirect, and total effects in multilevel models when all relevant variables are measured at Level 1 and all effects are random. Formulas are provided for the mean and variance of the indirect and total effects and for the sampling variances of the average indirect and total effects. Simulations show that the estimates are unbiased under most conditions. Confidence intervals based on a normal approximation or a simulated sampling distribution perform well when the random effects are normally distributed but less so when they are nonnormally distributed. These methods are further developed to address hypotheses of moderated mediation in the multilevel context. An example demonstrates the feasibility and usefulness of the proposed methods.

Adolescent↗
PubMed2005

Lumbar synovial cysts of the spine: an evaluation of surgical outcome.

OBJECTIVE: Our aim was to study the outcomes and results of surgically treated patients with synovial cysts of the lumbar spine in our institution. METHODS: Retrospective data from 39 consecutive patients, treated during the period of December 1996 to August 2004, were analyzed. Twenty-eight men (70%) and 11 women (30%) of mean age 63.3 years were studied. All pre- and postoperative signs, symptoms, extension/flexion radiographs, magnetic resonance imaging (MRI), and computed tomography (CT) with or without myelography were reviewed. All underwent surgery for synovial cysts with excision and decompression. Additional fusion in 26 patients was performed; 22 of them had degenerative spinal spondylolisthesis. Nine (23%) patients had prior decompression procedures, with three (8%) having had prior spinal instrumentation. Surgical outcomes were evaluated according to a questionnaire scoring system (scale of 1-4; 4 = excellent, 3 = good, 2 = fair, 1 = poor). Various preoperative attributes such as gender, age, weight, and height were analyzed to see if they had any effect on the outcome of surgery. Modified musculoskeletal outcomes data evaluation and management system (MODEM), questionnaire was provided to all; 24 (62%) responded. The following categories were determined: excellent (<20), very good (21-40), good (41-60), fair (61-80), and poor (81-100). Postoperative complications were also recorded. RESULTS: All patients had pain in their lower extremities, with 62% experiencing pain bilaterally. Ninety-five percent had pain in their back and 36% in the buttocks (36%). Eighteen (46%) patients had CT myelography. A total of 42 cysts were found. Two patients had bilateral cysts at L4-L5 level. Histology revealed two hemorrhagic cysts. The average duration of surgery was 231 minutes (range 92-391 minutes), and a mean blood loss of 930 mL (range 200-2500 mL) was recorded. Two operative dural tears and one postoperative wound dehiscence were observed. One patient had a recurrent synovial cyst at the site of original surgery. Eight patients (four each in the fusion and nonfusion group) had junctional degeneration and symptoms. A regression analysis performed on age, height, weight, and gender showed that they were not determining factors of surgical outcome. Surgery of spinal cysts at L4-L5 segment produced good and those at L5-S1 and multilevel excellent results. Patients with spinal segment fusion had superior outcomes, with 80% having excellent or good outcomes versus approximately 70% without fusion. With the modified MODEM questionnaire, 22 of the 24 (92%) patients scored between excellent, very good, and good. Two patients scored in the fair range, and none of the 24 patients scored in the range of poor. CONCLUSIONS: Spinal cysts are commonly found at the L4-L5 level, the site of maximum instability. MRI is the tool of choice for diagnosis. The etiology is still unclear, but underlying spinal instability has a strong association for formation of spinal cysts and worsening symptoms. Synovial cysts resistant to conservative therapy should be treated surgically. Resection and decompression with fusion remain an appropriate option. The optimal approach for patients with juxtafacet cysts remains unclear. The best surgical treatment approach for each particular individual appears to remain speculative.

Adult↗
PubMed2001

Comparing personal trajectories and drawing causal inferences from longitudinal data.

This review considers statistical analysis of data from studies that obtain repeated measures on each of many participants. Such studies aim to describe the average change in populations and to illuminate individual differences in trajectories of change. A person-specific model for the trajectory of each participant is viewed as the foundation of any analysis having these aims. A second, between-person model describes how persons very in their trajectories. This two-stage modeling framework is common to a variety of popular analytic approaches variously labeled hierarchical models, multilevel models, latent growth models, and random coefficient models. Selected published examples reveal how the approach can be flexibly adapted to represent development in domains as diverse as vocabulary growth in early childhood, academic learning, and antisocial propensity during adolescence. The review then considers the problem of drawing causal inferences from repeated measures data.

Adolescent↗