The humeroscapular motion interface

Motion between the humerus and scapula commonly is described as glenohumeral motion. However, humeroscapular motion occurs at two distinct sites. In addition to the motion at the diarthrodial glenohumeral joint, movement occurs between the proximal humerus and related structures and the surrounding sleeve of structures, including the acromion, deltoid, coracoid, coracoacromial ligament, and the muscles attached to the coracoid. This site of nonarticular shoulder motion is defined as the humeroscapular motion interface. Nonarticular humeroscapular motion can be documented and measured using standard magnetic resonance imaging techniques. The maximum average interfacial motion using axial images was 29.1 mm, which occurred at the level of the maximum diameter of the humeral head. Interfacial motion varied depending on the site measured. If pathologic conditions such as adhesions secondary to trauma or surgery interfere with or obliterate this space at sites of significant sliding motion, overall shoulder motion will be limited. Successful treatment of shoulder stiffness related to humeroscapular restraints is likely to require restoration of the normal sliding motion at the humeroscapular motion interface, in addition to resolving restraints affecting the glenohumeral joint motion.     

Cre/loxP-mediated excision and amplification of large segments of the Escherichia coli genome

The isolation and amplification of large, predetermined segments of a genome from its host have been explored. The prototype of our approach was the excisional replication of some viruses such as the lambda-lysogen. Similar machinery was used to excise and amplify large genomic segments of Escherichia coli in its host. Two loxP sequences for a site-specific recombinase Cre, together with a conditional replication origin (pi-dependent gamma-ori), were inserted into the genome by homologous recombination at predetermined sites, 50-100 kb apart. Cre and pir200 which encodes the site-specific recombinase Cre and an ori-specific replication protein pi, respectively, were also introduced into the genome. The predetermined genomic segments flanked by the loxP sequences were excised and amplified upon induction of the cre and pir200 genes which were under the control of the tet promoter. This excised and amplified DNA could be easily purified as a large plasmid. This procedure can provide an alternative to conventional cloning methods by obtaining predetermined large genomic segments directly from the original organisms. In this study, using the Cre/loxP site-specific recombination and pi/gamma-ori replication system of plasmid R6K, a procedure was devised that could isolate a large segment of the E. coli genome and demonstrated the feasibility of the procedure by excising and amplifying the 50-kb trg-narZ and 100-kb trg-hipA regions of the E. coli W3110 genome.     

Duration of human singleton pregnancies in Ibadan, Nigeria

Analysis of gestation length in an obstetric population of indigenous African women revealed a mean pregnancy duration of 274.8 days, which is similar to values recorded in women of African descent elsewhere, but about 1 week less than what generally has been reported in women of European ancestry and Japanese women. Factors associated with lower pregnancy duration among these women include increasing maternal age and gravidity, and the birth of a male infant. It is concluded that mean pregnancy duration in Nigerian women is shorter than the 280 days normally used in obstetric calculations. The consistent finding of a shorter length of gestation in these and other black women suggests earlier maturity of the fetoplacental unit. Earlier institution of antepartum fetal monitoring in women of African descent, particularly women > 30 years old and those with high parity, may reduce the risks of fetal morbidity and mortality attributable to postmaturity in their offspring.     

Effect of 0.1% dexamethasone on epithelial healing in experimental corneal alkali wounds: morphological changes during the repair process

To have the "power" of avoiding undersized clinical trials, the customary statistical strategy used in the past few decades is aimed at rejecting both a null stochastic hypothesis and a contradictory alternative hypothesis. This approach gives a trial the "power" to confirm the "insignificance" of differences much smaller than the large value of delta desired in trials done to show efficacy. In many instances, however, a prime problem is that the current "double-significance" approach produces sample sizes 2-3 times larger than needed for stochastic confirmation of large differences (> or =delta). The inflated sample sizes and consequent problems can be avoided if a realistic value for delta is chosen and maintained thereafter, and if an adequate "capacity" is calculated for "single significance."     

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.     

FEM application to loess slope excavation and support: case study of Dong Loutian coal bunker,Shuozhou, China

The largest coal bunker in China will be built in the Dong Loutian loess region to store coal, and the long V-shaped loess slope of the bunker, more than 60 m in depth, will be excavated. The finite element method of numerical simulation is applied (using linear elastic and hardening soil models) to simulate stability of the excavation slope and deformation with and without reinforcement, with a view to predict the deformation trend, design the reinforcement scheme, decrease the unrealistically large heave at the base of excavation and horizontal displacement of the excavation slope, and ensure the safety of the project. The simulation results show that the stress field redistributes after excavation and reinforcement, and the horizontal displacement of the slope is inhibited effectively, while the soil at the base of the bunker should be emphatically compacted and supported by piles. The field-measured data are in better agreement with the results calculated from the hardening-soil model and the combined support mode of anchor and soil nail. Thus, the results can be used to determine the key deformation range and reinforcing areas for engineering design.