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1.
Chem Commun (Camb) ; 60(35): 4663-4666, 2024 Apr 25.
Article in English | MEDLINE | ID: mdl-38591135

ABSTRACT

The response of the trimethylammonium-iodinechloride and diiodide (TMA-ICl/I2) crystal structures have been examined under high pressure using neutron powder diffraction. TMA-ICl exhibits impressive pressure-driven electronic flexibility, where the N⋯I-Cl interactions progressively encompass all the distances represented in analogous structures recorded in the Cambridge Structural Database. Comparison with the TMA-I2 complex reveals that this flexibility is owed to the electronegativity of the chlorine atom which induces increased distortion of the iodine electron cloud. This structural flexibility may be influential in the future design of functional molecular materials.

2.
Cureus ; 14(11): e31897, 2022 Nov.
Article in English | MEDLINE | ID: mdl-36579217

ABSTRACT

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has disrupted the world since 2019, causing significant morbidity and mortality in developed and developing countries alike. Although substantial resources have been diverted to developing diagnostic, preventative, and treatment measures, disparities in the availability and efficacy of these tools vary across countries. We seek to assess the ability of commercial artificial intelligence (AI) technology to diagnose COVID-19 by analyzing chest radiographs. MATERIALS AND METHODS: Chest radiographs taken from symptomatic patients within two days of polymerase chain reaction (PCR) tests were assessed for COVID-19 infection by board-certified radiologists and commercially available AI software. Sixty patients with negative and 60 with positive COVID reverse transcription-polymerase chain reaction (RT-PCR) tests were chosen. Results were compared against results of the PCR test for accuracy and statistically analyzed by receiver operating characteristic (ROC) curves along with area under the curve (AUC) values. RESULTS: A total of 120 chest radiographs (60 positive and 60 negative RT-PCR tests) radiographs were analyzed. The AI software performed significantly better than chance (p = 0.001) and did not differ significantly from the radiologist ROC curve (p = 0.78). CONCLUSION: Commercially available AI software was not inferior compared with trained radiologists in accurately identifying COVID-19 cases by analyzing radiographs. While RT-PCR testing remains the standard, current advances in AI help correctly analyze chest radiographs to diagnose COVID-19 infection.

3.
AJR Am J Roentgenol ; 219(6): 962-972, 2022 12.
Article in English | MEDLINE | ID: mdl-35792137

ABSTRACT

BACKGROUND. Despite evidence supporting the specificity of classic metaphyseal lesions (CML) for the diagnosis of child abuse, some medicolegal practitioners claim that CML result from rickets rather than trauma. OBJECTIVE. The purpose of this study was to evaluate radiologists' diagnostic performance in differentiating rickets and CML on radiographs. METHODS. This retrospective seven-center study included children younger than 2 years who underwent knee radiography from January 2007 to December 2018 and who had either rickets (25-hydroxyvitamin D level < 20 ng/mL and abnormal knee radiographs) or knee CML and a diagnosis of child abuse from a child abuse pediatrician. Additional injuries were identified through medical record review. Radiographs were cropped and zoomed to present similar depictions of the knee. Eight radiologists independently interpreted radiographs for diagnoses of rickets or CML, rated confidence levels, and recorded associated radiographic signs. RESULTS. Seventy children (27 girls, 43 boys) had rickets; 77 children (37 girls, 40 boys) had CML. Children with CML were younger than those with rickets (mean, 3.7 vs 14.2 months, p < .001; 89.6% vs 5.7% younger than 6 months; 3.9% vs 65.7% older than 1 year). All children with CML had injuries in addition to the knee CML identified at physical examination or other imaging examinations. Radiologists had almost perfect agreement for moderate- or high-confidence interpretations of rickets (κ = 0.92) and CML (κ = 0.89). Across radiologists, estimated sensitivity, specificity, and accuracy for CML for moderate- or high-confidence interpretations were 95.1%, 97.0%, and 96.0%. Accuracy was not significantly different between pediatric and nonpediatric radiologists (p = .20) or between less experienced and more experienced radiologists (p = .57). Loss of metaphyseal zone of provisional calcification, cupping, fraying, and physeal widening were more common in rickets than CML, being detected in less than 4% of children with CML. Corner fracture, bucket-handle fracture, subphyseal lucency, deformed corner, metaphyseal irregularity, and subperiosteal new bone formation were more common in CML than rickets, being detected in less than 4% of children with rickets. CONCLUSION. Radiologists had high interobserver agreement and high diagnostic performance for differentiating rickets and CML. Recognition that CML mostly occur in children younger than 6 months and are unusual in children older than 1 year may assist interpretation. CLINICAL IMPACT. Rickets and CML have distinct radiographic signs, and radiologists can reliably differentiate these two entities.


Subject(s)
Child Abuse , Fractures, Bone , Rickets , Male , Female , Humans , Child , Infant , Child, Preschool , Retrospective Studies , Rickets/diagnostic imaging , Radiography , Bone and Bones , Child Abuse/diagnosis , Fractures, Bone/diagnostic imaging , Radiologists
4.
J Pediatr Surg Case Rep ; 79: 102223, 2022 Apr.
Article in English | MEDLINE | ID: mdl-35223426

ABSTRACT

Symptomatic COVID-19 less frequently affects the pediatric population and is often associated with atypical presenting symptoms. Here we describe a nine-year-old patient who presented with acute hypoxic respiratory failure and was found to have perforated appendicitis, intra-abdominal abscess, and bronchoperitoneal fistula. The rapid progression of this pathology, complex critical care decision making, and ultimate surgical management has not been previously described. Documenting this patient's clinical course and effective treatments may serve to inform and guide the medical community and pediatric care providers as the world continues to combat the COVID-19 pandemic.

5.
Radiol Case Rep ; 16(11): 3341-3345, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34484542

ABSTRACT

Noninvasive reduction of ileocolic intussusception requires increasing intracolonic pressure via gas or liquid administered through a rectal catheter. A tight seal around the catheter is required to maintain intracolonic pressures and this tight seal is difficult to maintain with existing techniques. I describe the safe and effective use of a catheter with 2 balloons near the tip that surround the anus internally and externally to prevent leakage of air during an enema on a toddler after failure with a single-balloon tipped catheter.

6.
Proc Natl Acad Sci U S A ; 111(46): E4936-45, 2014 Nov 18.
Article in English | MEDLINE | ID: mdl-25369936

ABSTRACT

The arginyltransferase Ate1 is a component of the N-end rule pathway, which recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins, and thereby causes their degradation by the proteasome. At least six isoforms of mouse Ate1 are produced through alternative splicing of Ate1 pre-mRNA. We identified a previously uncharacterized mouse protein, termed Liat1 (ligand of Ate1), that interacts with Ate1 but does not appear to be its arginylation substrate. Liat1 has a higher affinity for the isoforms Ate1(1A7A) and Ate1(1B7A). Liat1 stimulated the in vitro N-terminal arginylation of a model substrate by Ate1. All examined vertebrate and some invertebrate genomes encode proteins sequelogous (similar in sequence) to mouse Liat1. Sequelogs of Liat1 share a highly conserved ∼30-residue region that is shown here to be required for the binding of Liat1 to Ate1. We also identified non-Ate1 proteins that interact with Liat1. In contrast to Liat1 genes of nonprimate mammals, Liat1 genes of primates are subtelomeric, a location that tends to confer evolutionary instability on a gene. Remarkably, Liat1 proteins of some primates, from macaques to humans, contain tandem repeats of a 10-residue sequence, whereas Liat1 proteins of other mammals contain a single copy of this motif. Quantities of these repeats are, in general, different in Liat1 of different primates. For example, there are 1, 4, 13, 13, 17, and 17 repeats in the gibbon, gorilla, orangutan, bonobo, neanderthal, and human Liat1, respectively, suggesting that repeat number changes in this previously uncharacterized protein may contribute to evolution of primates.


Subject(s)
Aminoacyltransferases/metabolism , Evolution, Molecular , Mice/genetics , Primates/genetics , Tandem Repeat Sequences , Alternative Splicing , Amino Acid Sequence , Animals , Arginine/metabolism , Base Sequence , Chromosome Mapping , Exons/genetics , Gene Expression , Humans , Ligands , Molecular Sequence Data , Protein Binding , Protein Isoforms/metabolism , Protein Processing, Post-Translational , Proteolysis , Recombinant Fusion Proteins/metabolism , Sequence Alignment , Sequence Homology , Species Specificity
7.
Stat Med ; 30(25): 3050-6, 2011 Nov 10.
Article in English | MEDLINE | ID: mdl-21805487

ABSTRACT

When a number of models are fit to the same data set, one method of choosing the 'best' model is to select the model for which Akaike's information criterion (AIC) is lowest. AIC applies when maximum likelihood is used to estimate the unknown parameters in the model. The value of -2 log likelihood for each model fit is penalized by adding twice the number of estimated parameters. The number of estimated parameters includes both the linear parameters and parameters in the covariance structure. Another criterion for model selection is the Bayesian information criterion (BIC). BIC penalizes -2 log likelihood by adding the number of estimated parameters multiplied by the log of the sample size. For large sample sizes, BIC penalizes -2 log likelihood much more than AIC making it harder to enter new parameters into the model. An assumption in BIC is that the observations are independent. In mixed models, the observations are not independent. This paper develops a method for calculating the 'effective sample size' for mixed models based on Fisher's information. The effective sample size replaces the sample size in BIC and can vary from the number of subjects to the number of observations. A number of error models are considered based on a general mixed model including unstructured, compound symmetry.


Subject(s)
Bayes Theorem , Cluster Analysis , Longitudinal Studies/statistics & numerical data , Likelihood Functions , Sample Size
8.
Diabetes Care ; 34(7): 1487-91, 2011 Jul.
Article in English | MEDLINE | ID: mdl-21593292

ABSTRACT

OBJECTIVE: Insulin detemir lacks the usual propensity for insulin to cause weight gain. We investigated whether this effect was a result of reduced energy intake and/or increased energy expenditure. RESEARCH DESIGN AND METHODS: A 32-week, randomized crossover design trial was undertaken in 23 patients with type 1 diabetes. Patients on a basal-bolus regimen (with insulin aspart as the bolus insulin) were randomly assigned to insulin detemir or NPH insulin as a basal insulin for 16 weeks, followed by the other basal insulin for 16 weeks. At the end of each 16-week period, total energy expenditure, resting energy expenditure, diet-induced thermogenesis, activity energy expenditure, energy intake, weight change, glycemic control, hypoglycemic episodes, and hormones that affect satiety and fuel partitioning were measured. RESULTS: After 16 weeks, weight change was -0.69±1.85 kg with insulin detemir and +1.7±2.46 kg with NPH insulin (P<0.001). Total energy intake was significantly less with insulin detemir (2,016±501 kcal/day) than with NPH insulin (2,181±559 kcal/day) (P=0.026). There was no significant difference in any measure of energy expenditure, HbA1c percentage, or number of hypoglycemic episodes. Leptin was lower and resistin was higher with insulin detemir compared with NPH insulin (P=0.039, P=0.047). After the meal, ghrelin and pancreatic polypeptide levels (P=0.002, P=0.001) were higher with insulin detemir. CONCLUSIONS: The reduced weight gain with insulin detemir compared with NPH insulin is attributed to reduced energy intake rather than increased energy expenditure. This may be mediated by a direct or indirect effect of insulin detemir on the hormones that control satiety.


Subject(s)
Diabetes Mellitus, Type 1/drug therapy , Hypoglycemic Agents/therapeutic use , Insulin, Isophane/therapeutic use , Insulin/analogs & derivatives , Weight Gain/drug effects , Adult , Blood Glucose/metabolism , Cross-Over Studies , Eating , Energy Intake , Female , Humans , Insulin/therapeutic use , Insulin Detemir , Insulin, Long-Acting , Male
9.
FASEB J ; 24(8): 2762-71, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20388698

ABSTRACT

Low birth weight is associated with glucose intolerance, insulin resistance, and type 2 diabetes (T2D) in later life. Good evidence indicates that the environment plays an important role in this relationship. However, the mechanisms underlying these relationships are defined poorly. Islets are particularly susceptible to oxidative stress, and this condition combined with fibrosis is thought to be instrumental in T2D pathogenesis. Here we use our maternal low-protein (LP) rat model to determine the effect of early diet on oxidative stress and fibrosis in pancreatic islets of male offspring at 3 and 15 mo of age. Islet xanthine oxidase (XO) expression was increased in 15-mo LP offspring, which suggests increased oxidative-stress. Manganese superoxide-dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), and heme oxygenase-1 (HO-1) (antioxidant enzymes) were reduced significantly in LP offspring, which indicated impairment of oxidative defense. Expression of fibrosis markers collagen I and collagen III also increased in 15-mo LP offspring. Angiotensin II receptor type I (AT(II)R(1)), induced by hyperglycemia and oxidative-stress, was significantly up-regulated in 15-mo LP offspring. Lipid peroxidation was also increased in 15-mo LP animals. We conclude that maternal protein restriction causes age-associated increased oxidative stress, impairment of oxidative defense, and fibrosis. These findings provide mechanisms by which suboptimal early nutrition can lead to T2D development later in life.


Subject(s)
Antioxidants/pharmacology , Fibrosis/etiology , Islets of Langerhans/pathology , Maternal Nutritional Physiological Phenomena , Oxidative Stress , Animals , Diabetes Mellitus, Type 2/etiology , Female , Male , Phenotype , Pregnancy , Prenatal Exposure Delayed Effects , Rats
10.
J Biol Chem ; 285(22): 17218-34, 2010 May 28.
Article in English | MEDLINE | ID: mdl-20356838

ABSTRACT

Our study of the mouse Ate1 arginyltransferase, a component of the N-end rule pathway, has shown that Ate1 pre-mRNA is produced from a bidirectional promoter that also expresses, in the opposite direction, a previously uncharacterized gene (Hu, R. G., Brower, C. S., Wang, H., Davydov, I. V., Sheng, J., Zhou, J., Kwon, Y. T., and Varshavsky, A. (2006) J. Biol. Chem. 281, 32559-32573). In this work, we began analyzing this gene, termed Dfa (divergent from Ate1). Mouse Dfa was found to be transcribed from both the bidirectional P(Ate1/Dfa) promoter and other nearby promoters. The resulting transcripts are alternatively spliced, yielding a complex set of Dfa mRNAs that are present largely, although not exclusively, in the testis. A specific Dfa mRNA encodes, via its 3'-terminal exon, a 217-residue protein termed Dfa(A). Other Dfa mRNAs also contain this exon. Dfa(A) is sequelogous (similar in sequence) to a region of the human/mouse HTEX4 protein, whose physiological function is unknown. We produced an affinity-purified antibody to recombinant mouse Dfa(A) that detected a 35-kDa protein in the mouse testis and in several cell lines. Experiments in which RNA interference was used to down-regulate Dfa indicated that the 35-kDa protein was indeed Dfa(A). Furthermore, Dfa(A) was present in the interchromatin granule clusters and was also found to bind to the Ggnbp1 gametogenetin-binding protein-1 and to the Abt1 activator of basal transcription that interacts with the TATA-binding protein. Given these results, RNA interference was used to probe the influence of Dfa levels in luciferase reporter assays. We found that Dfa(A) acts as a repressor of TATA-box transcriptional promoters.


Subject(s)
Aminoacyltransferases/metabolism , Gene Expression Regulation , Nuclear Proteins/metabolism , Repressor Proteins/metabolism , TATA Box , TATA-Box Binding Protein/metabolism , Transcription Factors, General/metabolism , Amino Acid Sequence , Animals , Base Sequence , Chromatin/metabolism , Humans , Male , Mice , Molecular Sequence Data , Promoter Regions, Genetic , Repressor Proteins/genetics , Sequence Homology, Amino Acid , Testis/metabolism
11.
Am Fam Physician ; 78(11): 1289-94, 2008 Dec 01.
Article in English | MEDLINE | ID: mdl-19069022

ABSTRACT

Varicose veins are twisted, dilated veins most commonly located on the lower extremities. Risk factors include chronic cough, constipation, family history of venous disease, female sex, obesity, older age, pregnancy, and prolonged standing. The exact pathophysiology is debated, but it involves a genetic predisposition, incompetent valves, weakened vascular walls, and increased intravenous pressure. A heavy, achy feeling; itching or burning; and worsening with prolonged standing are all symptoms of varicose veins. Potential complications include infection, leg ulcers, stasis changes, and thrombosis. Some conservative treatment options are avoidance of prolonged standing and straining, elevation of the affected leg, exercise, external compression, loosening of restrictive clothing, medical therapy, modification of cardiovascular risk factors, reduction of peripheral edema, and weight loss. More aggressive treatments include external laser treatment, injection sclerotherapy, endovenous interventions, and surgery. Comparative treatment outcome data are limited. There is little evidence to preferentially support any single treatment modality. Choice of therapy is affected by symptoms, patient preference, cost, potential for iatrogenic complications, available medical resources, insurance reimbursement, and physician training.


Subject(s)
Exercise Therapy/methods , Sclerotherapy/methods , Stockings, Compression , Varicose Veins/therapy , Vascular Surgical Procedures/methods , Humans , Treatment Outcome
12.
Metabolism ; 57(11): 1608-14, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18940401

ABSTRACT

Although low-density lipoprotein (LDL) cholesterol is often normal in patients with type 2 diabetes mellitus, there is evidence for a reduced fractional catabolic rate and consequently an increased mean residence time (MRT), which can increase atherogenic risk. The dyslipidemia and insulin resistance of type 2 diabetes mellitus can be improved by aerobic exercise, but effects on LDL kinetics are unknown. The effect of 6-month supervised exercise on LDL apolipoprotein B kinetics was studied in a group of 17 patients with type 2 diabetes mellitus (mean age, 56.8 years; range, 38-68 years). Patients were randomized into a supervised group, who had a weekly training session, and an unsupervised group. LDL kinetics were measured with an infusion of 1-(13)C leucine at baseline in all groups and after 6 months of exercise in the patients. Eight body mass index-matched nondiabetic controls (mean age, 50.3 years; range, 40-67 years) were also studied at baseline only. At baseline, LDL MRT was significantly longer in the diabetic patients, whereas LDL production rate and fractional clearance rates were significantly lower than in controls. Percentage of glycated hemoglobin A(1c), body mass index, insulin sensitivity measured by the homeostasis model assessment, and very low-density lipoprotein triglyceride decreased (P < .02) in the supervised group, with no change in the unsupervised group. After 6 months, LDL cholesterol did not change in either the supervised or unsupervised group; but there was a significant change in LDL MRT between groups (P < .05) that correlated positively with very low-density lipoprotein triglyceride (r = 0.51, P < .04) and negatively with maximal oxygen uptake, a measure of fitness (r = -0.51, P = .035), in all patients. The LDL production and clearance rates did not change in either group. This study suggests that a supervised exercise program can reduce deleterious changes in LDL MRT.


Subject(s)
Apolipoproteins B/metabolism , Cholesterol, LDL/metabolism , Diabetes Mellitus, Type 2/metabolism , Exercise , Adult , Aged , Body Mass Index , Female , Glycated Hemoglobin/analysis , Humans , Insulin Resistance , Lipoproteins, VLDL/metabolism , Male , Middle Aged , Oxygen Consumption , Triglycerides/metabolism
13.
Prostate ; 68(6): 620-8, 2008 May 01.
Article in English | MEDLINE | ID: mdl-18213632

ABSTRACT

OBJECTIVES: Due to specific physiological functions, prostatic tissues and fluids have unique metabolic profiles. In this study, proton nuclear magnetic resonance spectroscopy ((1)H-NMRS) is used to assess potential metabolic markers of prostate cancer (PCa) in human expressed prostatic secretions (EPS). METHODS: Metabolic profiles of EPS from 52 men with PCa and from 26 healthy controls were analyzed using quantitative (1)H-NMRS. The metabolites quantified included citrate, spermine, myo-inositol, lactate, alanine, phosphocholine, glutamine, acetate, and hydroxybutyrate. Logistic regression (LR) was used to model the risk of PCa based on metabolite concentrations while adjusting for age. RESULTS: The average age of the EPS donors with PCa was 58.0+/-7.0 years and 52.2+/-12.1 for the healthy donors. The median Gleason score for the men with PCa was 7 (range 5-9). The LR models indicated that the absolute concentrations of citrate, myo-inositol, and spermine were highly predictive of PCa and inversely related to the risk of PCa. The areas under the receiver operating characteristic curves (AUROC) for citrate, myo-inositol and spermine were 0.89, 0.87, and 0.79, respectively. At 90% sensitivity, these metabolites had specificities of 74%, 51%, and 34%, respectively. The LR analysis indicated that absolute levels of these three metabolites were independent of age. CONCLUSIONS: The results indicate that citrate, myo-inositol and spermine are potentially important markers of PCa in human EPS. Further, the absolute concentrations of these metabolites in EPS appear to be independent of age, increasing the potential utility of these markers due to elimination of age as a confounding variable.


Subject(s)
Aging/metabolism , Biomarkers, Tumor/metabolism , Citric Acid/metabolism , Inositol/metabolism , Prostate/metabolism , Spermine/metabolism , Adult , Aged , Area Under Curve , Body Fluids/chemistry , Citric Acid/analysis , Humans , Inositol/analysis , Magnetic Resonance Spectroscopy , Male , Metabolism , Middle Aged , ROC Curve , Spermine/analysis
14.
Biom J ; 49(3): 416-28, 2007 Jun.
Article in English | MEDLINE | ID: mdl-17623346

ABSTRACT

We propose a state space model for analyzing equally or unequally spaced longitudinal count data with serial correlation. With a log link function, the mean of the Poisson response variable is a nonlinear function of the fixed and random effects. The random effects are assumed to be generated from a Gaussian first order autoregression (AR(1)). In this case, the mean of the observations has a log normal distribution. We use a combination of linear and nonlinear methods to take advantage of the Gaussian process embedded in a nonlinear function. The state space model uses a modified Kalman filter recursion to estimate the mean and variance of the AR(1) random error given the previous observations. The marginal likelihood is approximated by numerically integrating out the AR(1) random error. Simulation studies with different sets of parameters show that the state space model performs well. The model is applied to Epileptic Seizure data and Primary Care Visits Data. Missing and unequally spaced observations are handled naturally with this model.


Subject(s)
Clinical Trials as Topic/statistics & numerical data , Models, Statistical , Algorithms , Data Interpretation, Statistical , Longitudinal Studies , Normal Distribution , Public Health Informatics , Software
15.
J Eval Clin Pract ; 12(5): 583-90, 2006 Oct.
Article in English | MEDLINE | ID: mdl-16987121

ABSTRACT

OBJECTIVE: To evaluate the effects of organizational change and sharing of specialist skills and information technology for diabetes in two primary care groups (PCGs) over 4 years. METHODS: In PCG-A, an intervention comprised dedicated specialist sessions in primary care, clinical guidelines, educational meetings for professionals and a shared diabetes electronic patient record (EPR). Comparison was made with the neighbouring PCG-B as control. In intervention and control PCGs, practice development work was undertaken for a new contract for family doctors. Data were collected for clinical measures, practice organizational characteristics and professional and patient views. RESULTS: Data were analysed for 26 general practices including 17 in PCG-A and nine in PCG-B. The median practice-specific proportions of patients with HbA1c recorded annually increased in both areas: PCG-A from median 65% to 77%, while PCG-B from 53% to 84%. For cholesterol recording, PCG-A increased from 50% to 76%, and PCG-B from 56% to 80%. Organizational changes in both PCGs included the establishment of recall systems, dedicated clinics and educational sessions for patients. In both PCGs, practices performing poorly at baseline showed the greatest improvements in organization and clinical practice. Primary care professionals' satisfaction with access and communication with diabetes specialist doctors and nurses increased, more so in the intervention PCG. Only 16% of primary care professional respondents used the diabetes EPR at least monthly. Patient satisfaction and knowledge did not change. CONCLUSIONS: Improvements in practices' organizational arrangements were associated with improvements in clinical care in both PCGs. Sharing specialist skills in one PCG was associated with increased professional satisfaction but no net improvement in clinical measures. A shared diabetes EPR is unlikely to be used, unless integrated with practice information systems.


Subject(s)
Diabetes Mellitus/therapy , Group Practice/organization & administration , Medicine , Specialization , Urban Population , England , Health Personnel/psychology , Humans , Longitudinal Studies , Medical Record Linkage , Medical Records Systems, Computerized , Patient Satisfaction , Surveys and Questionnaires
16.
Biom J ; 48(3): 411-9, 2006 Jun.
Article in English | MEDLINE | ID: mdl-16845905

ABSTRACT

Longitudinal data usually consist of a number of short time series. A group of subjects or groups of subjects are followed over time and observations are often taken at unequally spaced time points, and may be at different times for different subjects. When the errors and random effects are Gaussian, the likelihood of these unbalanced linear mixed models can be directly calculated, and nonlinear optimization used to obtain maximum likelihood estimates of the fixed regression coefficients and parameters in the variance components. For binary longitudinal data, a two state, non-homogeneous continuous time Markov process approach is used to model serial correlation within subjects. Formulating the model as a continuous time Markov process allows the observations to be equally or unequally spaced. Fixed and time varying covariates can be included in the model, and the continuous time model allows the estimation of the odds ratio for an exposure variable based on the steady state distribution. Exact likelihoods can be calculated. The initial probability distribution on the first observation on each subject is estimated using logistic regression that can involve covariates, and this estimation is embedded in the overall estimation. These models are applied to an intervention study designed to reduce children's sun exposure.


Subject(s)
Biometry/methods , Data Interpretation, Statistical , Likelihood Functions , Logistic Models , Longitudinal Studies , Signal Processing, Computer-Assisted , Computer Simulation , Markov Chains , Time Factors
17.
Prev Med ; 42(3): 162-70, 2006 Mar.
Article in English | MEDLINE | ID: mdl-16376977

ABSTRACT

BACKGROUND: This study evaluated the behavioral impact of a skin cancer prevention program in which health care providers delivered advice and materials to parents of infants over a 3-year period from 1998 to 2001. METHODS: Fourteen offices of a large managed care organization in Colorado were randomly assigned to the intervention or control groups. 728 infants and their parents were recruited within 6 months of birth. At intervention offices, health care providers attended orientation sessions, prompts for delivering sun protection advice were placed in medical records, and parents received sun protection packets at each well-child visit between 2 and 36 months of age. RESULTS: Based on provider self-report and exit interviews of parents, providers in the intervention group delivered approximately twice as much sun protection advice as providers in the control group. Annual telephone interviews of parents indicated small but statistically significant differences in parent sun protection practices favoring the intervention. Skin exams revealed no significant differences in tanning, freckling, or number of nevi. Behavioral differences between groups appeared to grow over the 3 years of follow-up. CONCLUSIONS: This intervention strategy was successful in increasing the delivery of sun protection advice by health care providers and resulted in changes in parents' behaviors. While the behavioral effect was probably not strong enough to reduce risk for skin cancer, the effect may increase as children age and have more opportunities for overexposure to the sun.


Subject(s)
Child Welfare , Health Behavior , Health Education/methods , Parents/education , Skin Neoplasms/prevention & control , Sunlight/adverse effects , Adolescent , Adult , Child, Preschool , Colorado , Education, Medical, Continuing , Female , Health Maintenance Organizations , Humans , Infant , Interviews as Topic , Male , Pamphlets , Parents/psychology , Pediatrics/education , Pediatrics/methods , Physical Examination , Physician-Patient Relations , Skin Neoplasms/etiology , Sunburn/prevention & control
18.
Acta Crystallogr A ; 61(Pt 6): 568-74, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16244406

ABSTRACT

The purpose of this paper and a test case study is to assess a method of ab initio structure solution from powder diffraction data using f' difference techniques. A theoretical foundation for the approach used is first provided. Then, with a test case (nickel sulfate hexahydrate), it is shown that both the position of the anomalous scatterer (Ni) can be determined and the structure can be developed in full. Specifically, synchrotron-radiation data were collected at two wavelengths close to the K edge for Ni and three wavelengths remote from the Ni absorption edge, at 1.3, 1.8 and 2.16 A. These five wavelengths then allowed various combinations to be tried to establish which wavelength pairs gave the optimum signal in the Patterson maps using dispersive amplitude differences. The initial phases derived from the metal-atom position then allowed the structure to be fully developed by difference Fourier cycling. The relevance of these developments to structure-solution possibilities for proteins via powder dispersive difference data is then outlined.

19.
J Nutr ; 135(9): 2159-65, 2005 Sep.
Article in English | MEDLINE | ID: mdl-16140892

ABSTRACT

The role of ingested fat in the etiology of obesity is controversial. The aims of this study were to determine the contributions of ingested fat oxidation to: 1) 24-h total energy expenditure (TEE), and 2) substrate oxidation during acute stationary cycle exercises in adult humans. Healthy, moderately obese (n = 18; BMI = 31 +/- 1 kg/m2) subjects (8 men; 10 women) were each studied in a whole-room calorimeter for 24 h. They were fed mixed meals (55, 30, and 15% as energy from carbohydrate, fat and protein, respectively) to maintain energy balance. Each subject performed 1255-kJ cycle exercises at 50% VO2max in the calorimeter. Study test meal fat was labeled with carbon-13 (13C). Ingested fat oxidation was estimated from breath 13CO2 excretion and the subject's chamber CO2 production. Total fat and carbohydrate oxidations were estimated from nonprotein respiratory quotient (NP-RQ) values. Endogenous fat oxidation was estimated as the difference between total fat and ingested fat oxidations. TEE was estimated from gas exchanges; 28 +/- 3% of ingested fat was oxidized and it provided 8 +/- 1% of 24-h TEE. During cycle exercises, ingested fat provided 50% of total fat oxidized and 13.0 +/- 2% of energy expended. Endogenous fat oxidation contributed 10.4 +/- 3% of energy expenditure during cycle exercises. This study extended to 24-h observations of previous studies that lasted 6-9 h on ingested fat oxidation in humans. Understanding the factors that promote ingested fat oxidation could lead to more effective obesity intervention programs.


Subject(s)
Circadian Rhythm , Dietary Fats/metabolism , Energy Metabolism , Obesity/metabolism , Adult , Bicycling , Body Composition , Carbon Dioxide , Female , Humans , Male , Oxidation-Reduction , Pulmonary Gas Exchange , Respiration , Severity of Illness Index
20.
Clin Orthop Relat Res ; (422): 145-7, 2004 May.
Article in English | MEDLINE | ID: mdl-15187848

ABSTRACT

Long-term follow-up of twenty-six patients with unicameral bone cysts treated by curettage and packing with plaster-of-Paris pellets showed a recurrence in only two cases and no serious complications.


Subject(s)
Bone Cysts/surgery , Calcium Sulfate/therapeutic use , Femur , Adolescent , Adult , Bone Cysts/diagnostic imaging , Child , Child, Preschool , Cohort Studies , Curettage/methods , Female , Follow-Up Studies , Humans , Male , Radiography , Retrospective Studies , Risk Assessment , Treatment Outcome
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