A comparison of tooth-borne and bone-anchored expansion devices in SARME.

PURPOSE: Major adult maxillary transverse discrepancies are usually treated with surgically assisted rapid maxillary expansion (SARME), utilizing a combination of surgical and orthodontic techniques. Unfortunately, a consensus has not been reached on topics ranging from the best surgical technique that should be performed to the ideal expander type that should be installed. The present study sought to evaluate the efficiency and stability of the maxillary expansion achieved with two types of expanders following the same SARME procedure without pterygomaxillary disjunction (PMD). METHODS: Twenty-four patients with a maxillary transverse deficiency were enrolled in the study. All patients underwent the same SARME, and 12 received a bone-anchored (KLS Martin®) and 12 were installed with a tooth-borne (Hyrax®) expander. Dental impressions were collected both preoperatively and 1 year postoperatively. These casts were scanned and the distances between specific interdental and intergingival points were measured and analyzed. Statistical analyses were performed to assess the effects expander type had on the efficiency of the maxillary expansion and long-term stability. RESULTS: Expansion in the anterior maxillary and premolar regions was found to be similar in both groups. In contrast, the tooth-borne device resulted in a significantly greater expansion in the molar region. CONCLUSION: The SARME technique without PMD is highly effective at treating adults with maxillary transverse deficiencies, and the type of expander selected depends on the location of the larger maxillary constriction region of each patient.

Genetically encoded self-assembly of large amyloid fibers.

"Functional" amyloids are found throughout nature as robust materials. We have discovered that "template" and "adder" proteins cooperatively self-assemble into micrometer-sized amyloid fibers with a controllable, hierarchical structure. Here, Escherichia coli is genetically engineered to express a template protein, Gd20, that can initiate self-assembly of large amyloid fibrils and fibers. Through atomic force microscopy (AFM) we found that expression of Gd20 produces large amyloid fibrils of 490 nm diameter and 2-15 µm length. Addition of an extracellular adder protein, myoglobin, continues self-assembly to form amyloid tapes with widths of ∼7.5 µm, heights of ∼400 nm, and lengths exceeding 100 µm. Without myoglobin the amyloid fibrils are metastable over time. When myoglobin is present, the amyloid fiber continues self-assembling to a width of ∼18 µm and height of ∼1 µm. Experimental results demonstrate that large amyloid fibers with a tailored stiffness and morphology can be engineered at the DNA level, spanning four orders of magnitude.

Polymer Mechanics as a Model for Short-Term and Flow-Independent Cartilage Viscoelasticity.

Articular cartilage is the load bearing soft tissue that covers the contacting surfaces of long bones in articulating joints. Healthy cartilage allows for smooth joint motion, while damaged cartilage prohibits normal function in debilitating joint diseases such as osteoarthritis. Knowledge of cartilage mechanical function through the progression of osteoarthritis, and in response to innovative regeneration treatments, requires a comprehensive understanding of the molecular nature of interacting extracellular matrix constituents and interstitial fluid. The objectives of this study were therefore to (1) examine the timescale of cartilage stress-relaxation using different mechanistic models and (2) develop and apply a novel (termed "sticky") polymer mechanics model to cartilage stress-relaxation based on temporary binding of constituent macromolecules. Using data from calf cartilage samples, we found that different models captured distinct timescales of cartilage stress-relaxation: monodisperse polymer reptation best described the first second of relaxation, sticky polymer mechanics best described data from ∼1-100 seconds of relaxation, and a model of inviscid fluid flow through a porous elastic matrix best described data from 100 seconds to equilibrium. Further support for the sticky polymer model was observed using experimental data where cartilage stress-relaxation was measured in either low or high salt concentration. These data suggest that a complete understanding of cartilage mechanics, especially in the short time scales immediately following loading, requires appreciation of both fluid flow and the polymeric behavior of the extracellular matrix.

Cartilage stress-relaxation is affected by both the charge concentration and valence of solution cations.

OBJECTIVE: Understanding the mechanical functions of specific cartilage molecules such as aggrecan is important for understanding both healthy cartilage and disease progression. Cartilage is primarily composed of chondrocytes and an extracellular matrix consisting of multiple biopolymers, ions, and water. Aggrecan is one matrix biopolymer which consists of a core protein and multiple anionic glycosaminoglycans. Previous research has demonstrated that the stiffness of extracted aggrecan decreases under increased solution cation concentration, and the purpose of this study was to determine whether changes in solution ion concentration resulted in changes in tissue-level viscoelastic properties. METHODS: Middle-zone explants of bovine calf patellofemoral cartilage were harvested and cultured overnight before mechanical testing. Repeated stress-relaxation and cyclical loading tests were performed after equilibration in solutions of 0.15 M and 1 M NaCl and 0.075 M and 0.5 M CaCl(2). A stretched exponential model was fit to the stress-relaxation data. Storage and loss moduli were determined from the cyclical loading data. RESULTS: Changes in ionic strength and species affected both stress-relaxation and cyclical loading of cartilage. Stress-relaxation was faster under higher ionic strength. CaCl(2) concentration increases resulted in decreased peak stress, while NaCl increases resulted in decreased equilibrium stress. Storage and loss moduli were affected differently by NaCl and CaCl(2). CONCLUSIONS: These results show that cartilage stress-relaxation proceeds faster under higher concentrations of solution cations, consistent with the theory of polymer dynamics. These data demonstrate the complexity of cartilage mechanical properties and suggest that aggrecan stiffness may be important in tissue-level cartilage viscoelastic properties.

Climatic unpredictability and parasitism of caterpillars: implications of global warming.

Insect outbreaks are expected to increase in frequency and intensity with projected changes in global climate through direct effects of climate change on insect populations and through disruption of community interactions. Although there is much concern about mean changes in global climate, the impact of climatic variability itself on species interactions has been little explored. Here, we compare caterpillar-parasitoid interactions across a broad gradient of climatic variability and find that the combined data in 15 geographically dispersed databases show a decrease in levels of parasitism as climatic variability increases. The dominant contribution to this pattern by relatively specialized parasitoid wasps suggests that climatic variability impairs the ability of parasitoids to track host populations. Given the important role of parasitoids in regulating insect herbivore populations in natural and managed systems, we predict an increase in the frequency and intensity of herbivore outbreaks through a disruption of enemy-herbivore dynamics as climates become more variable.

Polymer dynamics as a mechanistic model for the flow-independent viscoelasticity of cartilage.

The initial, rapid, flow independent, apparent stress relaxation of articular cartilage disks deformed by unconfined compressive displacement is shown to be consistent with the theory of polymer dynamics. A relaxation function for polymers based upon a mechanistic model of molecular interaction (reptation) appropriately approximated early, flow independent relaxation of stress. It is argued that the theory of polymer dynamics, with its reliance on mechanistic models of molecular interaction, is an appropriate technique for application to and the understanding of rapid, flow independent, stress relaxation in cartilage.

Emergency department visits by demented patients with malfunctioning feeding tubes.

BACKGROUND: Objective data indicate that feeding tubes in demented patients may not be efficacious and can have serious complications, but no study characterizes emergency department resource utilization for these patients. This study aimed to evaluate the incidence and resource utilization related to feeding tube malfunction in demented patients visiting the emergency department. METHODS: A retrospective chart review for all demented patients visiting the emergency department with malfunctioning feeding tubes from September 1999 to May 2001 was conducted. Demographic data, diagnoses, type of tube, length of emergency department stay, method of transportation to the emergency department, consultations, laboratory evaluation, x-ray data, and total hospital and ambulance charges were determined. RESULTS: A total of 138 emergency department visits by 33 patients occurred during this period (range of visits per patients, 1-21; mean, 4.1 +/- 4.3). Malfunctions occurred in 61 percutaneous endoscopically placed gastric tubes, 37 jejunostomy tubes, 34 gastric tubes, 4 endoscopically placed gastrostomy and jejunostomy tubes, and 2 percutaneous endoscopically placed jejunostomy tubes. This required 108 ambulance round-trips to and from the emergency department. The most frequent complication was unintentional dislodgement (n = 125). The average length of stay was 2.6 +/- 1.6 h. All the patients were seen by an emergency department physician. In addition, there were 99 surgical and 26 gastroenterology consultations about these patients. The total hospital charges, not including physician fees, were 86,234.48 dollars, and the total reimbursement (actual) from Medicare for ambulance charges was 57,664.00 dollars. During the same 21-month period, 42 feeding tubes were placed for dementia. CONCLUSIONS: The expense of emergency department visits for tube dislodgment or malfunction is a previously unreported issue involved in the tube feeding of demented patients. Extrapolation of our data yields an estimated health care charge of almost $11 million for the country per year.

Comparative pharmacology of proton pump inhibitors.

The PPIs are the most effective therapy to suppress gastric acid secretion. These agents decrease acid secretion by inhibiting parietal cell proton pumps. From chemical and pharmacodynamic points of view, subtle differences that exist among the PPIs may influence clinical activity.

Retrospective analysis of the effects of cisapride on the QT interval and QT dispersion in chronic hemodialysis patients.

Cisapride is contraindicated in patients with end-stage renal disease (ESRD) and gastrointestinal motility disorders. Ventricular arrhythmias have been associated with both cisapride and hemodialysis (HD). However, reports conflict regarding the safety of cisapride in HD patients. We undertook this study to characterize the effects of cisapride on QT intervals and QT dispersion (QTD) in HD patients. Baseline and steady-state electrocardiograms (ECGs) were retrospectively selected for calendar year 1999 for each patient administered cisapride if ECGs showed sinus rhythm, potassium level was 3.5 mEq/dL or greater, and there was no pharmacokinetic drug interaction. QT intervals were measured by two investigators, and QTDs were calculated (maximum [QT(max)] - minimum QT interval [QT(min)]). Averages between investigator measures (+/- SD), presented for each value, were evaluated using Wilcoxon's signed-rank test. Thirty-one HD patients were administered cisapride. Seventeen patients failed to meet entry criteria, and no patient had a pharmacokinetic drug interaction. In included patients (6 men, 8 women), heart rates were 86.71 +/- 20.87 beats/min at baseline and 86.57 +/- 14.23 beats/min during treatment (P = not significant). Serum potassium levels were 4.97 +/- 1.2 mEq/dL at baseline and 4.94 +/- 0.76 mEq/dL during treatment (P = not significant). Average baseline QT(max) and QT(min) were 391.07 +/- 42.43 and 330.71 +/- 40.94 milliseconds, respectively. Treatment QT(max) and QT(min) were 391.43 +/- 38.2 and 343.93 +/- 35.69 milliseconds, respectively (P = not significant for both). QTD was 60.36 +/- 17.59 milliseconds at baseline and 47.5 +/- 19.59 milliseconds during treatment (P = 0.074). Mean corrected QT (QTc) intervals increased from 426.57 +/- 26.62 to 431.71 +/- 29.98 milliseconds (P = 0.55) from baseline to treatment. No ventricular arrhythmia was observed during at least 160 days (range, 2 to 830 days) of cisapride exposure. Two patients died during this study, both of other causes 4 days after discontinuing cisapride therapy. Cisapride did not significantly increase mean QTc interval, QT(max), or QTD in patients with ESRD managed by HD when potassium levels were stable and pharmacokinetic drug interactions were avoided.

Routine perioperative pulmonary artery catheterization has no effect on rate of complications in vascular surgery: a meta-analysis.

Despite widespread use pulmonary artery catheterization has not been proven to reduce complications or mortality. One study supported the use of routine preoperative pulmonary artery catheterization in moderate-risk vascular surgery patients; several other studies have reported that pulmonary artery catheterization is not efficacious. Our goal was to scrutinize the data using meta-analysis. This is a systematic review of the literature. MEDLINE was searched for all articles on pulmonary artery catheterization, optimization, oxygen delivery, and preoperative preparation of vascular surgery patients. Data from papers judged appropriate for inclusion were analyzed using a computer program, Easy MA. Complications were defined as only those that could have reasonably have been prevented by or resulted from pulmonary artery catheterization. Of hundreds of possible papers only four were found to be adequate randomized prospective studies with similar exclusions, therapeutic endpoints, and interpretable complication and mortality rates. Controls included 174 patients versus 211 in the protocol group. Power analysis showed that the combined sample sizes were adequate. The meta-analysis demonstrates that the studies are homogeneous. The use of a pulmonary artery catheter does not prevent morbidity or mortality. Of the studies providing data on the amount of intravenous fluid administered three reported that statistically significantly more fluid was given to patients who underwent pulmonary artery catheterization. Meta-analysis indicates that in moderate-risk vascular surgery patients routine preoperative pulmonary artery catheterization is not associated with improved outcomes.

Management of penile toilet seat injury--report of two cases.

Blunt trauma to the penis is an uncommon injury in young children. We present two cases of blunt penile trauma secondary to mechanical compression from a toilet seat.

Use of cyanoacrylate tissue adhesive under a diaper.

OBJECTIVE: To examine the utility of cyanoacrylate tissue adhesive (Dermabond, Ethicon, Somerville, NJ, USA; an effective means of epithelial skin closure) under a diaper (i.e. constantly exposed to bodily fluids) in 25 children (not toilet-trained) undergoing inguinal surgery. PATIENTS AND METHODS: A retrospective review of charts between July 1998 and July 2000 was used to identify children who were not toilet-trained and who had undergone inguinal surgery (e.g. orchidopexy, hernia and hydrocele repair). In addition to the type of surgery, the method of closure was also assessed; in all cases reported the subcutaneous tissues were approximated with 4/0 polyglactin suture. From July 1998 to October 1999 all epithelial skin was closed with 5/0 poliglecaprone, benzoin, sterile strips and collodion; from October 1999 to July 2000 all skin was closed with cyanoacrylate tissue adhesive. RESULTS: The chart review identified 45 boys (mean age 15.3 months, range 1-26) of whom 26 (57%) had undergone either inguinal hernia or hydrocele repair, and 19 (42%) who had undergone orchidopexy. These procedures resulted in a total of 52 incisions in the 45 children. Of the 52 incisions, 27 were closed with suture and 25 with cyanoacrylate adhesive. All patients were followed up at 2 weeks; there were no instances of infection or wound dehiscence in either group. The incisions were cosmetically identical at 3 months of follow-up. CONCLUSION: Cyanoacrylate adhesive is a safe and effective method of skin closure that can be used under a diaper.

Utility of biofeedback for the daytime syndrome of urinary frequency and urgency of childhood.

OBJECTIVES: To evaluate in a preliminary study the utility of biofeedback for the treatment of the daytime syndrome of urinary frequency and urgency of childhood, a benign, self-limited condition with symptoms that can last for months or years. Observation is a commonly recommended approach to this syndrome because medications and other forms of therapy are often not effective. METHODS: During a 2-year period, 89 children (34 boys and 55 girls) presented with this syndrome. Patient age ranged from 4 to 11 years, and duration of symptoms ranged from 1 to 38 months. All children were evaluated with a history, physical examination, urinalysis and culture, and renal and bladder ultrasound scanning. After the evaluation, the parents were offered either observation or surface patch electromyography biofeedback for the problem. RESULTS: Overall, 84 parents (94.3%) selected biofeedback for their child. After 1 month of biofeedback, 34.5% of children were able to achieve a 2 to 4-hour voiding interval. After 2 to 4 months of biofeedback, another 51.2% of patients experienced the same improvement. Overall, 85.7% of children who underwent biofeedback had symptom improvement. In 14.3% of children, no symptom improvement was noted after 4 months of biofeedback and these children were considered nonresponders. CONCLUSIONS: The results of this study suggest that biofeedback may be a treatment option for this disorder and warrants further investigation.

Impact of presentation of research results on likelihood of prescribing medications to patients with left ventricular dysfunction.

This study was conducted to evaluate willingness to prescribe medication based on identical data presented in different outcome terms to health professionals of varied discipline, geographic location, and level of training. Cross-sectional survey using a self-administered questionnaire was performed in 400 health professionals (physicians, pharmacists, physicians-in-training, and pharmacy students) in the United States and Europe. Data reflecting a clinical trial were presented in 6 outcome terms: 3 terms describing identical mortality (relative risk reduction, absolute risk reduction, and number of patients needed to be treated to prevent 1 death); and 3 distractors (increased life expectancy, decreased hospitalization rate, and decreased cost). Willingness to prescribe and rank order of medication preference assuming willingness to prescribe were measured. The results of the study showed that willingness to prescribe and first choice preference were significantly greater when study results were presented as relative risk reduction than when identical mortality data were presented as absolute risk reduction or number of patients needed to be treated to avoid 1 death (p <0.001). Increase in life expectancy was the most influential distractor. In conclusion, this study, performed in the era of "evidence-based medicine," demonstrates that the method of reporting research trial results has significant influence on health professionals' willingness to prescribe. The high numerical value of relative risk reduction and the concrete and tangible quality of increased life expectancy exert greater influence on health professionals than other standard outcome terms.