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PubMed2022

Significant variation in the performance of DNA methylation predictors across data preprocessing and normalization strategies.

BACKGROUND: DNA methylation (DNAm)-based predictors hold great promise to serve as clinical tools for health interventions and disease management. While these algorithms often have high prediction accuracy, the consistency of their performance remains to be determined. We therefore conduct a systematic evaluation across 101 different DNAm data preprocessing and normalization strategies and assess how each analytical strategy affects the consistency of 41 DNAm-based predictors. RESULTS: Our analyses are conducted in a large EPIC DNAm array dataset from the Jackson Heart Study (N = 2053) that included 146 pairs of technical replicate samples. By estimating the average absolute agreement between replicate pairs, we show that 32 out of 41 predictors (78%) demonstrate excellent consistency when appropriate data processing and normalization steps are implemented. Across all pairs of predictors, we find a moderate correlation in performance across analytical strategies (mean rho = 0.40, SD = 0.27), highlighting significant heterogeneity in performance across algorithms. Successful or unsuccessful removal of technical variation furthermore significantly impacts downstream phenotypic association analysis, such as all-cause mortality risk associations. CONCLUSIONS: We show that DNAm-based algorithms are sensitive to technical variation. The right choice of data processing strategy is important to achieve reproducible estimates and improve prediction accuracy in downstream phenotypic association analyses. For each of the 41 DNAm predictors, we report its degree of consistency and provide the best performing analytical strategy as a guideline for the research community. As DNAm-based predictors become more and more widely used, our work helps improve their performance and standardize their implementation.

DNA Methylation↗
PubMed2004

Vestibular processing in human paramedian precuneus as shown by electrical cortical stimulation.

The authors describe a 16-year-old patient with recurrent episodes of epileptic linear self-motion perception and occasional body tilts. Intracranial seizure monitoring located the seizure onset, caused by a circumscribed ependymoma, in the right paramedian precuneus. Electrical cortical stimulation of this area could reproduce the same vestibular sensations, which ceased after lesionectomy. The findings implicate the paramedian area of the precuneus in the processing of static and dynamic vestibular, probably otolithic, information.

Adolescent↗
PubMed2004

Dragonfly flight: free-flight and tethered flow visualizations reveal a diverse array of unsteady lift-generating mechanisms, controlled primarily via angle of attack.

Here we show, by qualitative free- and tethered-flight flow visualization, that dragonflies fly by using unsteady aerodynamic mechanisms to generate high-lift, leading-edge vortices. In normal free flight, dragonflies use counterstroking kinematics, with a leading-edge vortex (LEV) on the forewing downstroke, attached flow on the forewing upstroke, and attached flow on the hindwing throughout. Accelerating dragonflies switch to in-phase wing-beats with highly separated downstroke flows, with a single LEV attached across both the fore- and hindwings. We use smoke visualizations to distinguish between the three simplest local analytical solutions of the Navier-Stokes equations yielding flow separation resulting in a LEV. The LEV is an open U-shaped separation, continuous across the thorax, running parallel to the wing leading edge and inflecting at the tips to form wingtip vortices. Air spirals in to a free-slip critical point over the centreline as the LEV grows. Spanwise flow is not a dominant feature of the flow field--spanwise flows sometimes run from wingtip to centreline, or vice versa--depending on the degree of sideslip. LEV formation always coincides with rapid increases in angle of attack, and the smoke visualizations clearly show the formation of LEVs whenever a rapid increase in angle of attack occurs. There is no discrete starting vortex. Instead, a shear layer forms behind the trailing edge whenever the wing is at a non-zero angle of attack, and rolls up, under Kelvin-Helmholtz instability, into a series of transverse vortices with circulation of opposite sign to the circulation around the wing and LEV. The flow fields produced by dragonflies differ qualitatively from those published for mechanical models of dragonflies, fruitflies and hawkmoths, which preclude natural wing interactions. However, controlled parametric experiments show that, provided the Strouhal number is appropriate and the natural interaction between left and right wings can occur, even a simple plunging plate can reproduce the detailed features of the flow seen in dragonflies. In our models, and in dragonflies, it appears that stability of the LEV is achieved by a general mechanism whereby flapping kinematics are configured so that a LEV would be expected to form naturally over the wing and remain attached for the duration of the stroke. However, the actual formation and shedding of the LEV is controlled by wing angle of attack, which dragonflies can vary through both extremes, from zero up to a range that leads to immediate flow separation at any time during a wing stroke.

Animals↗
PubMed1988

The blood vascular architecture of the extra-adrenal chromaffin body in the adult rat: a scanning electron microscopic study of corrosion casts.

A well developed extra-adrenal chromaffin body with an axis of 200-400 micron was found in seven out of thirty adult male Wistar rats under a stereomicroscope. All seven bodies were located between the left and right kidneys. Blood vascular beds of the five bodies were reproduced with a methacrylate casting medium and observed with a scanning electron microscope. It was revealed that the extra-adrenal chromaffin body contained remarkedly numerous capillaries, which anastomosed with each other to form a conglomerated network. The blood capillaries were of small and uniform caliber and did not represent swollen sinusoids as in the adrenal medulla. The capillary network was denser than that in the adrenal medulla and had no direct vascular linkage with the adrenal cortex or an extra-adrenal cortical body. Histological examination of the two bodies treated with dichromate containing fixatives confirmed that they mainly consisted of chromaffin cells. These findings suggest that in the rat, extra-adrenal chromaffin bodies survive throughout life, actively producing catecholamines.

Adrenal Cortex↗
PubMedDate not supplied

Weighing up the risks.

Explore the source record for details and available documents.

Community Mental Health Services↗
PubMed1991

[Examination of coordination of masseter muscle activity].

The coordination of masseter muscle contraction is inseparably wrapped up in the occlusal elements. This study measured bilaterally the masseter muscle activity of 22 subjects without temporomandibular joint disease. The EMG recordings of the left and the right masseter muscles were repeated 20 times to test symmetry, reproducibility and appearance of silent periods. In 6 subjects the beginning of the muscle contraction showed laterality characteristics depending on handedness. The complex processes of recorded mandibular movements showed more biological variations than the recording patterns of occlusal indicator foils may disclose. That indicates the possibility of pseudocontact markings. The occluding surfaces therefore should allow free mandibular movements.

Adult↗
PubMed1996

[Is the presence of right ventricular high intensity signals sufficient for the diagnosis of right ventricular dysplasia?].

The aim of this study was to assess "morphological" MRI data (spin-echo) compared with cine-MRI in 10 patients with documented right ventricular dysplasia and 10 normal controls. Data was acquired with a 0.5 Tesla superconductor magnet associating sequences of spin-echo and gradient echo (cine-MRI). An abnormal high intensity signal was observed in spin-echo in 9 out of the 10 patients. They were present on the anterior and sub-tricuspid walls of the right ventricle (8/10) and in the pulmonary infundibulum (8/10). A dyskinetic zone corresponding to the abnormal signals was detected in 8 patients. In the control group, only one subject had an abnormal high intensity signal and no dyskinesis could be detected. The association of high intensity signals and dyskinesis would seem to be very specific of right ventricular dysplasia. On the other hand, a high intensity signal alone may be observed in apparently normal subjects and would seem to be less specific.

Aged↗
PubMed2003

[Laparoscopic right hemicolectomy with intracorporeal anastomosis. Technical aspects and personal experience].

BACKGROUND: Laparoscopic colo-rectal surgery has gained wide acceptance as a treatment in a variety of benign and malignant diseases. The reproducibility and safety of all the principal colo-rectal procedures has been demonstrated, but some indications are still controversial. A great part of surgeons perform right hemicolectomy by laparo-assisted technique and consider it more difficult than left hemicolectomy. METHODS: A retrospective analysis of a series of 180 laparoscopic colon resections performed between 1994 and 2001 is presented. Surgical indications were: 46 cases of benign disorders and 134 colonic malignancy. The right hemicolectomy were 27 (15%): 2 benign and 25 malignant diseases. The technical aspects of completely laparoscopic right hemicolectomy is described in details. A completely mechanical intra-corporeal anastomosis is always performed. To remove the bowel specimen from the abdominal cavity it is put it in a large bag and pull it out of a 3-4 cm enlargement of a trocar-site (in the umbilical scar). RESULTS: Data of the 27 laparoscopic right hemicolectomy were analysed: there was 1 conversion to open surgery; no intra-operative complications were observed; the postoperative period was complicated by 1 anastomotic fistula. The median operative time was of 150 minutes. No case of port-site recurrence was observed. CONCLUSIONS: The laparoscopic colo-rectal surgery can reproduce in selected patients, the techniques performed in open surgery with minimally invasive treatment. It is possible to perform a completely laparoscopic right hemicolectomy after an adequate training in advanced laparoscopy, anyway there are many advantages: less postoperative pain, short-term postoperative ileus, earlier return to daily activity.

Adult↗
PubMed1998

A comparison of curvatures of left and right hand movements in a simple pointing task.

Human arm movements towards visual targets are remarkably reproducible in several tasks and conditions. Various authors have reported that trajectories of unconstrained point-to-point movements are slightly curved, smooth and have bell-shaped velocity profiles. The hand paths of such movements show small - but significant - curvatures throughout the workspace. The cause of these curvatures is still obscure. Traditionally this curvature is explained as the result of an optimisation process or is ascribed to mechanical or dynamic properties of the effector system. Recently, however, it has been suggested that these curvatures are due at least partly, to the visual misperception of straight lines. To evaluate the latter hypothesis, we compared unconstrained, self-paced point-to-point movements that subjects made with their right and left hand. We assume that the visual misperception may depend on the position in the workspace, subject, etc. but not on the hand used to make the movement. Therefore we argue that if curvature is caused by a visual misperception of straight lines, curvatures should be the same for movements made with the left and right hand. Our experiments cast strong doubt on the hypothesis that curvatures are the result of a visual distortion, because curvatures of the left hand trajectories, mirrored in the mid-sagittal plane, are found to be accurately described by trajectories of the right hand. Estimates of the effect of visual distortion on movement curvature show that, if present, this effect is very small compared with other sources that contribute to movement curvature. We found that curvatures depend strongly on the subject and on the direction and distance of the movement. Curvatures do not seem to be caused purely by the dynamic properties of the arm, since curvatures do not change significantly with increasing movement velocity. Therefore, we conclude that curvatures reflect an inherent property of the control of multi-joint arm movements.

Adult↗
PubMed2004

Memory for time intervals is impaired in left hemi-Parkinson patients.

The basal ganglia have been proposed as one of the neural correlates of timekeeping functions. Both encoding and memory retrieval components for time perception are impaired in Parkinson's disease (PD). The aim of our study was to investigate in hemi-Parkinsonian patients the existence of a specific alteration in memory for time depending on the affected side, to better understand the contribution of the left or right basal ganglia circuits in different components of time perception. Right and left hemi-PD patients performed a time reproduction task in which they were required to reproduce in the same session short (5 s) and long (15 s) time intervals, in off- and on-therapy condition. While the right hemi-PD patients overestimated the shorter interval, only the left hemi-PD group showed the memory migration effect, overestimating the shorter and underestimating the longer time intervals. These results argue for a critical involvement of the right basal ganglia in memory retrieval for time intervals, in the range of seconds.

Aged↗
PubMed1999

Simple single-section method for measurement of left and right atrial volumes with electron-beam CT.

RATIONALE AND OBJECTIVES: The authors estimated left and right atrial volumes by using a simple method of measurement with nonenhanced electron-beam computed tomography (CT). MATERIALS AND METHODS: One hundred sixty-four contrast material-enhanced electron-beam CT studies were divided into two groups. Group 1, which included 104 studies, was used to develop the measurement method (i.e., the formulas) for measuring left and right atrial volumes from a nonenhanced study. Group 2 consisted of 60 studies on which the validity of the method was tested. Measurement of left and right atrial volumes was performed on all section levels by tracing the respective atrial borders for each section, then multiplying the area by section thickness and summing the resultant volumes. RESULTS: Calculated left and right atrial volumes were derived by using the biggest atrial area and cephalic-caudal span. The span was equal to section thickness times the number of sections in which the atria were present. Linear regression analysis formulas were acquired with the biggest atrial area and cephalic-caudal span. Left and right atrial calculated volumes were obtained with these formulas and demonstrated a significant good relation (r > .95, P < .001) and a difference of less than 11% (P < .05) in absolute values between measured and calculated volumes. Intraobserver, interobserver, and interstudy reproducibility were excellent, with less than 10% difference in absolute values. CONCLUSION: Left and right atrial volumes can be accurately estimated from a single midventricular section by using nonenhanced electron-beam CT.

Anatomy, Cross-Sectional↗
PubMed2003

The case for regulating collaborative reproduction: a children's rights perspective.

There is little regulation of collaborative reproduction--the use of the eggs, sperm, or embryos of a third party to create a child biologically unrelated to at least one intending parent. This Article argues that the dearth of regulation should be assessed from a children's rights perspective and accordingly adjusted. After examining the effects of the experimental reproductive technologies, it concludes that traditional family law preferences and policies are undercut by the deliberate creation of collaboratively reproduced children. The lack of regulation might stem from constitutional protection afforded parents in the right of privacy and substantive due process cases. The author, however, contends that collaborative reproduction implicates the rights of children and requires a separate balancing of rights not contemplated in other cases. Collaborative reproduction also requires regulation because of its spill over effects on the acceptability of cloning. The Article concludes by offering several possible regulatory responses to the problems posed by collaborative reproduction.

Child↗
PubMed1996

Measurement of optic nerve blood flow with nonradioactive colored microspheres in rabbits.

The objective of this study was to establish a nonradioactive technique to accurately assess blood flow in a small tissue such as the anterior optic nerve. Colored microspheres, 10.2 +/- 0.23 microns in diameter, were injected into the left atrium in each of 17 anesthetized rabbits. The rabbits were divided into four groups injected, respectively, with 5, 10, 50, or 100 million microspheres. Microsphere quantification in the tissue was performed after postmortem dissection and alkaline corrosion of the anterior optic nerve. Blood flow was evaluated by means of reference sample comparison method. While the relative interocular difference (range, 15.3-162.8%) was not significantly different between the rabbits injected with 5, 10, or 50 million microspheres (Kruskal-Wallis test, P = 0.11), injection with 100 million microspheres yielded a significantly lower relative interocular differences (range 2.3-12.8%) compared to the other three groups (Kruskal-Wallis test, P = 0.0048). In addition, reproducibility of microsphere counts was evaluated by ranking the difference between right and left optic nerve in percentage of the average number of microspheres per milligram of tissue in both optic nerves. The correlation between the relative interocular difference (range, 2.3-162.8%) and the average number of microspheres per milligram of tissue (1.2-78.7 microspheres/mg optic nerve tissue) was statistically significant (Spearman R, -0.90; P < 0.0001). The interocular variability in microsphere counts and interocular difference in intraocular pressure did not correlate (Spearman R, 0.33; P = 0.20). The rabbits injected with 100 million microspheres showed the highest average number of microspheres (range, 31.8-78.7 microspheres/mg optic nerve tissue). The optic nerve blood flow ranged between 0.14 and 0.24 microliters/mg/min among the rabbits injected with 100 million microspheres. The present experimental technique of optic nerve blood flow measurement is relatively inexpensive, highly reproducible, and obviates disposal of radioactive materials.

Animals↗
PubMed1998

[Acoustic quantification of right ventricular dimensions and systolic function].

In view of the important prognostic significance of right ventricular systolic function, there have been many non-invasive studies of this subject. The majority of these studies have been limited by difficulties in modelisation of this geometrically complex cardiac chamber. Automatic border detection by acoustic quantification based on the back scatter of ultrasound provides a "direct" method of analysing right ventricular dimensions and functions. The authors undertook a prospective study of 34 patients to evaluate the reliability of this technique in measuring the surfaces and fractional shortening of the right ventricle. The feasibility was 92%. The correlation coefficients between the manual two-dimensional technique and automatic border detection were 0.81 for the end diastolic surface areas, 0.85 for the end systolic surface areas and 0.74 for the fractional shortening. Compared with the isotopic ejection fraction, the correlation coefficient was 0.73. The authors conclude that acoustic quantification is a feasible and reliable technique of measuring right ventricular dimensions and its contractile function.

Adult↗
PubMed1986

Covariant defects in visuospatial abilities and recall of verbal narrative after right hemisphere stroke.

Eighteen patients with right hemisphere strokes and 10 age-matched normal controls were tested for visuospatial abilities and for recall of brief narrative passages. Visuospatial and verbal abilities were evaluated using an objective scoring protocol that quantified accuracy in reproducing individual details, appreciation of structural relationships, and the appearance of unwarranted intrusions. The right hemisphere damaged group was found to be impaired on all measures of verbal recall. Across subjects these defects, particularly the inability to abstract information from the narrative passages, correlated with the degree of constructional apraxia. Analysis of CT scans failed to define a discrete region of the right hemisphere selectively associated with either the visuospatial or verbal defects, but indicated that both are exacerbated by the presence of premorbid brain atrophy.

Aged↗
PubMed2000

Quantification of right and left ventricular function by cardiovascular magnetic resonance.

Cardiac dysfunction is a major cause of cardiovascular morbidity and mortality. Accurate and reproducible assessment of cardiac function is essential for the diagnosis, the assessment of prognosis and evaluation of a patient's response to therapy. Cardiovascular Magnetic Resonance (CMR) provides a measure of global and regional function that is not only accurate and reproducible but is noninvasive, free of ionising radiation, and independent of the geometric assumptions and acoustic windows that limit echocardiography. With the advent of faster scanners, automated analysis, increasing availability and reducing costs, CMR is fast becoming a clinically tenable reference standard for the measurement of cardiac function.

Echocardiography↗