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At least 73 records · Page 4Linked to original sources

Unmanaged care: the need to regulate new reproductive technologies in the United States.

In the aftermath of allegations of the misuse of human eggs in the United States, questions are being raised about whether profitable reproductive services should continue to function in a free market under the aegis of physicians or should be regulated. Other countries in which reproductive technologies are employed to a significant degree have developed regulations governing their use, many as a result of recommendations made by inter-disciplinary commissions that solicited public input. Policy makers in the United States have been reluctant to regulate reproductive technologies, however, because their use is politically controversial, they want to whittle down government, some do not consider infertility an illness, and some believe regulation would interfere with the right to reproduce. Yet the unfettered use of reproductive technologies can create such harms as lack of informed consent, providing procedures not medically indicated for financial gain, practice by unqualified personnel, injury to patients and donors, failure to screen donated gametes, and inadequate medical record keeping. Americans place special value on the welfare of children and those who bring them into the world. Such values can outweigh individual procreative liberty when new reproductive technologies are at issue. Although the optimal course would be to establish a regulatory body to govern reproductive technologies, this is not politically feasible now. The newly established National Bioethics Advisory Commission provides a forum in which issues surrounding reproductive technologies should be addressed at this time in the United States.

Advisory Committees↗

On the birth of an infant with sickle cell anemia.

This is the first report in the English literature of the birth of an obligate SS infant whose parents both had sickle cell anemia. The young adult SS parents of this infant and their families did not wish to prevent the birth of this child but had, in fact, many positive reasons to continue the pregnancy to term even in the face of the increased personal risk of pregnancy for this mother. This unusual circumstance initiated a re-appraisal of the realistic expectations with respect to reproduction in patients with homozygous recessive genetic disorders. No definitive studies could be found which attempted to evaluate the influence of genetic counseling on reproductive behavior in patients with sickle cell anemia. The questions raised about the 'right to reproduce' and the realistic aims of genetic counseling in adult homozygote patients have been discussed. However, no conclusions seem warranted because of the paucity of available information.

Adult↗

Medical marijuana: should minors have the same rights as adults?

After reviewing the pertinent scientific data, it is clear that there is more than sufficient medical and ethical evidence to warrant the Bush Administration to authorize the Drug Enforcement Agency to reclassify marijuana as a Schedule II drug so that it can be used for medical purposes. Failure to give an effective therapy to seriously ill patients, either adults or children, violates the core principles of both medicine and ethics. Medically, to deny physicians the right to prescribe to their patients a therapy that relieves pain and suffering violates the physician-patient relationship. Ethically, failure to offer an available therapy that has proven to be effective violates the basic ethical principle of nonmaleficence, which prohibits the infliction of harm, injury, or death and is related to the maxim primum non nocere ('above all, or first, do no harm'), which is widely used to describe the duties of a physician. Therefore, in the patient's best interest, patients and parents/surrogates, have the right to request medical marijuana under certain circumstances and physicians have the duty to disclose medical marijuana as an option and prescribe it when appropriate. The right to an effective medical therapy, whose benefits clearly outweigh the burdens, must be available to all patients including children. To deny children the use of medical marijuana when appropriate is a grave injustice which violates the basic foundational beliefs of both medicine and

Child↗

QRS width in right bundle branch block. Accuracy and reproducibility of manual measurement.

BACKGROUND: The QRS prolongation and its relation to malignant ventricular arrhythmias are topics of interest. Controversies exist about the methodology of measuring the QRS. The aim of this study was to assess the accuracy and reproducibility of manual measurement of the QRS in standard electrocardiograms in patients with right bundle branch block and compare results with computer reading. METHODS AND RESULTS: Five experienced cardiologists at different levels of training were required to measure QRS duration in 30 electrocardiograms with different degrees of right bundle branch block collected from 24 randomly selected patients who had had radical repairs of tetralogy of Fallot. In each set of electrocardiograms there were six records which had been duplicated. The observers were neither told the purpose of the study nor how the electrocardiograms had been obtained, nor informed that some of the electrocardiograms were duplicates. Photocopies were identified by number, covering the patient's name and computerised measurement. Significant differences were found in the measurement of QRS in the same ECG calculated twice by the same observer (with an absolute variation up to 50 ms), within different observers (P=0.037) and measured manually or by computer (P=0.019). The width of the QRS did not influence the measurements as the biggest intra-observer variation (50 ms) was observed for relatively wide complex (median value between the two measurements 155 ms) and the biggest inter-observer (60 ms) for narrow complex (median value between the five measurements 110 ms). The QRS morphology appeared to influence the measurements, as the intra- and inter-observer variations were more consistent in the presence of obvious notching, slurrings and terminal slow vectors. CONCLUSIONS: Measurement of QRS is difficult, can be operator dependent and influenced by the presence of conduction abnormalities which reduce its accuracy and reproducibility.

Bundle-Branch Block↗

Facilitation of sustained bundle branch reentry by atrial fibrillation.

An electrophysiologic evaluation was performed in a patient with an idiopathic dilated cardiomyopathy and syncope. Ventricular tachycardia was not inducible despite the use of a variety of pacing maneuvers during sinus rhythm. Only after the electrical induction of atrial fibrillation did sustained bundle branch reentrant tachycardia (with both right and left bundle branch block QRS configurations) spontaneously occur and become reproducibly induced during right ventricular pacing. Ablation of the right bundle branch eliminated reproducibility of the tachycardia.

Aged↗

Reproducibility of MRI-derived measurements of right ventricular volumes and myocardial mass.

Magnetic resonance (MR) imaging has been shown to provide accurate measurements of right ventricular (RV) volumes and myocardial mass. The purpose of this study was to evaluate the reproducibility of MR imaging, which in clinical practice may be as important as its absolute accuracy. The reproducibility of MR imaging measurements of the right ventricle was assessed by analyzing 40 serial functional MR imaging examinations of the right ventricle with variance component analysis. Standard deviations and 95% ranges for change were: for RV myocardial mass, 5.9 and 16 g; and for RV ejection fraction, 6.0% and 16%, respectively. Reproducibility was similar for cine and spin-echo MR imaging. The intraobserver and interobserver errors were especially large, indicating that observer subjectivity is the limiting factor in the interpretation of the MR images. This study suggests that the reproducibility of RV measurements is adequate to detect RV hypertrophy and a low ejection fraction in the individual patient. For accurate follow-up examinations, whereby smaller changes are to be detected, the reproducibility of MR imaging measurements may not be sufficient. More effort is needed to improve the reproducibility of MR imaging measurements.

Adult↗

EEG correlates of coordinate processing during intermanual transfer.

Goal-directed movements require mapping of target information to patterns of muscular activation. While visually acquired information about targets is initially encoded in extrinsic, object-centered coordinates, muscular activation patterns are encoded in intrinsic, body-related coordinates. Intermanual transfer of movements previously learned with one hand is accomplished by the recall of unmodified extrinsic coordinates if the task is performed in original orientation. Intrinsic coordinates are retrieved in case of mirror-reversed orientation. In contrast, learned extrinsic coordinates are modified during the mirror movement and intrinsic coordinates during the originally oriented task. To investigate the neural processes of recall and modification, electroencephalogram (EEG) recording was employed during the performance of a figure drawing task previously trained with the right hand in humans. The figure was reproduced with the right hand (Learned-task) and with the left hand in original (Normal-task) and mirror orientations (Mirror-task). Prior to movement onset, beta-power and alpha- and beta-coherence decreased during the Normal-task as compared with the Learned-task. Negative amplitudes over fronto-central sites during the Normal-task exceeded amplitudes manifested during the Learned-task. In comparison to the Learned-task, coherences between fronto-parietal sites increased during the Mirror-task. Results indicate that intrinsic coordinates are processed during the pre-movement period. During the Normal-task, modification of intrinsic coordinates was revealed by cerebral activation. Decreased coherences appeared to reflect suppressed inter-regional information flow associated with utilization of intrinsic coordinates. During the Mirror-task, modification of extrinsic coordinates induced activation of cortical networks.

Adult↗

Measurement of right ventricular volume using cine computed tomography.

Volume measurements of the right ventricle are clinically important, particularly in the assessment of congenital heart disease. The complex configuration of the right ventricular cavity, however, makes assessment of its volume difficult. Cine computed tomography (CT) permits depiction of cardiac anatomy in parallel, sequential, high-resolution tomographic images. To test whether cine CT would allow accurate, reproducible determination of right ventricular volumes, 11 excised, fixed canine hearts were scanned ex vivo. The endocardial contours of the right ventricular cavity were traced by two independent observers. The right ventricular cavity areas were measured in each image and right ventricular volume calculated by a Simpson's rule approximation. Actual right ventricular volume (range 24-86.5 mL) was measured by cavity fluid capacity. Right ventricular volumes derived from cine CT data correlated closely with actual volumes (R = .96, cine CT volume = 0.99 X [actual volume] + 0.2 mL). Interobserver correlation was excellent (R = .99). It is concluded that cine CT scanning permits accurate, reproducible determination of right ventricular volume ex vivo. This technique should be immediately applicable to the noninvasive evaluation of right ventricular function in children and adults.

Animals↗

MR imaging of pulmonary hypertension and right ventricular dysfunction.

Right ventricular cardiac function is altered by abnormalities affecting primarily the left-sided cardiac structures, the lungs, or the right-sided cardiac structures themselves. The most common cardiac causes for right ventricular dysfunction are chronic left ventricular ischemia and rheumatic mitral valvular disease. Pulmonary diseases that result in right ventricular dysfunction include pulmonary air-space disease, including emphysema, and pulmonary interstitial and parenchymal diseases, including idiopathic pulmonary fibrosis and cystic fibrosis. Chronic pulmonary vascular disease, including chronic thromboembolism and PPH have a significant effect on right ventricular performance. Common to all of these diseases is elevation of pulmonary vascular resistance with a commensurate increase in right ventricular pressure, resulting in right ventricular hypertrophy. The limited ability of right ventricular myocardium to function in the face of increased pulmonary resistance results in right ventricular dilatation, tricuspid regurgitation, and ultimately right ventricular failure. MR imaging provides direct, noninvasive visualization of the right ventricular chamber as well as the myocardium itself, allowing reliable demonstration of morphologic changes in the size and shape of the ventricle, thickness of the myocardium, and presence of abnormal infiltration by fat or edema. Furthermore, because MR imaging techniques do not depend upon geometric assumptions about the complex shape of the right ventricle, they may be used for accurate and reproducible quantitation of right ventricular volume and myocardial mass.

Heart↗

Reproducibility of patch test results: a concurrent right-versus-left study using TRUE Test.

Wide variations in the reproducibility rate of positive patch test responses have been reported. We hypothesized that a major source of non-reproducibility resides in the methodological pitfalls of routine patch testing. Simultaneous duplicate patch testing on opposite sides of the upper back was performed on 500 consecutive patients, using the TRUE Test system consisting of 2 panels, each one containing 12 standard allergens. A rigorous methodological design was applied and relevance was assessed for all discordant patch test reactions. A total of 435 positive patch test reactions were observed either on one or both sides in 289 patients (58.8%). Of these, 22 (5%) were discordant, i.e. interpreted as positive allergic on one side whilst negative or doubtful on the opposite side. The allergens responsible for discordant reactions were nickel sulfate (4 patients), cobalt chloride (3), lanolin alcohol (3), fragrance mix (2), carba mix (2), thiuram mix (2), colophonium (1), potassium dichromate (1), p-phenylenediamine (1), formaldehyde (1), balsam of Peru (Myroxylon pereirae resin) (1) and thimerosal (1). Of the 19 (4%) patients with discordant patch test reactions, the allergen was deemed to be of definite present or past relevance in 9 patients (1.8% of the total and 3.1% of all patients with positive patch test reactions) and of possible relevance in a further 2 patients. These data suggest that patch testing is a reasonably reproducible procedure as long as methodological error is minimized.

Adolescent↗

Does antidromic activation of nociceptors play a role in sciatic radicular pain?

We describe a case where transcutaneous electrical stimulation of the right sciatic nerve in a patient with right L5 radiculopathy reproduced the patient's pathological pain in the leg. Following a right ankle block with 0.5% bupivacaine, the sciatic nerve stimulation induced pain in the thigh and the calf but not in the foot. Despite an increase in the magnitude of stimulation by 50% (compared with the stimulation before the block) the pain was not perceived below the level of blockade. We suggest that in this case the electrical stimulation generated impulses propagated antidromically into the leg and activated nociceptors in it. The bupivacaine blockade prevented antidromic propagation of impulses into the foot, therefore pain in this region was not perceived.

Female↗

Reproducibility of pulsed wave tissue Doppler echocardiography.

Four hundred and eighty paired recordings obtained from 16 patients (55 +/- 10 yrs; 10 men, 6 women) were analyzed to determine the reproducibility of both acquiring and measuring myocardial velocities recorded by tissue Doppler echocardiography. To assess intraobserver variability, 1 observer recorded and measured the data twice, from the same patients, and to assess interobserver variability, patients were examined by 2 independent observers. For the left ventricle, intraobserver reproducibility was higher when assessing long-axis velocities (+/- 10% to 16%) than short-axis velocities (+/- 14% to 24%). For the right ventricle, intraobserver reproducibility was high for the tricuspid annulus (+/- 9% to 15%), but unsatisfactory for the right ventricular anterior wall (+/- 21% to 25%). The highest interobserver reproducibilities were obtained for systolic and diastolic velocities of the lateral mitral annulus (+/- 9% to 17%) and systolic velocity of the tricuspid annulus (+/-13%). Interobserver reproducibility of the ratio of early-to-late peak diastolic velocities was very low for all investigated sites (+/- 20% to 52%). With the use of current techniques and software, reproducibility of acquiring and measuring tissue Doppler echocardiography is suboptimal for both systolic and diastolic myocardial velocities.

Echocardiography, Doppler↗

A field model of left-right asymmetries in the pattern regulation of a cell.

Dynamical models can offer insights into important aspects of patterns that recur throughout the biological world, such as global symmetries, mirror images, and pattern reversals, etc. Building on phenomenological rules of pattern formation (e.g. E. M. Nelsen and J. Frankel, 1986, Dev. Biol. 114, 53), the author developed a mathematical model of a morphogenetic field, expressed as a vector field, which contains the information to specify a pattern. The dynamics of the field arises from the minimization of a nonlinear energy density functional, a quartic polynomial of the field together with field gradient effects. This model was successfully applied in detail to surface patterns observed in right-handed Tetrahymena, where reproducible regions of left- and right-handed domains appear during regulation. Counterpart experiments on left-handed patterned cells suggest an intrinsic asymmetry between right- and left-handed patterning in this biological system, causing left-handed cells to follow different regulation pathways from the right-handed cells. We show that the energy minimization approach can account for this globally different behaviour in a version of the model with small local asymmetry.

Animals↗

Perception of movement patterns: tracking of movement.

The tracking of complex two-dimensional movement patterns was studied. Subjects were blindfolded, and their right hand moved around stencil patterns in the midsagittal plane, while the left hand concurrently reproduced the right-hand movement. The accuracy with which the left hand shadowed the criterion movements of the right hand was measured in shape and size. Right-hand movements were active or passive. Present tracking performance was contrasted with errors in recall reported by Bairstow and Laszlo (1978). Results showed that tracking performance was accurate. Active and passive criterion movements were tracked differently. Tracking was clearly superior to recall performance.

Journal Article↗

Modulating factors of calcium-free contraction at low [MgATP]: a physiological study on the steady states of skinned fibres of frog skeletal muscle.

Factors that modulate Ca(2+)-free contraction at low [MgATP] were examined by analysing steady tension development in skinned fibres of frog skeletal muscle. The commonly accepted bell-shaped relationship between steady tension and log (1/[MgATP]) was found to be highly susceptible to subtle experimental conditions at the higher [MgATP] side (right limb). The limb shifted to the right with increased fibre thickness, interrupted stirring of the bathing solution, increased temperature and fibre extension, although the effects of temperature and extension were marked only in thick fibres (cross-sectional area > 6000 microns 2). The shift of the right limb was reproduced by an addition of ADP to the bathing solution. These results, together with the extreme steepness of the right limb in thick fibres, suggest that a diffusion-dependent self-regenerative activation occurs in thick fibres in which ADP accumulation and ATP depletion positively feed back through further activation of the myofibrillar ATPase. Numerical simulation supported the hypothesis of the self-regenerative activation under poor diffusion conditions, and suggested that a small rise in temperature and fibre extension can trigger the self-regenerative process at the right limb. Consequently, ADP, temperature and fibre extension are deduced to be the primary potentiators of the activation at low [MgATP]. The high efficiency of ADP in shifting the limb suggests that the activating efficiency of the MgADP-bound actomyosin complex is higher than the nucleotide-free actomyosin complex.

Actomyosin↗

Quantitative fMRI assessment of the differences in lateralization of language-related brain activation in patients with temporal lobe epilepsy.

Defining language lateralization is important to minimize morbidity in patients treated surgically for temporal lobe epilepsy (TLE). Functional magnetic resonance imaging (fMRI) offers a promising, noninvasive, alternative strategy to the Wada test. Here we have used fMRI to study healthy controls and patients with TLE in order to (i) define language-related activation patterns and their reproducibility; (ii) compare lateralization determined by fMRI with those from of the Wada test; and (iii) contrast different methods of assessing fMRI lateralization. Twelve healthy right-handed controls and 19 right-handed preoperative patients with TLE (12 left- and seven right-TLE) were studied at 3T using fMRI and a verbal fluency paradigm. A Wada test also was performed on each of the patients. Greater activation was found in several areas in the right hemisphere for the left-TLE group relative to controls or right-TLE patients. Relative hemispheric activations calculated based on either the extent or the mean signal change gave consistent results showing a more bihemispheric language representation in the left-TLE patients. There was good agreement between the Wada and fMRI results, although the latter were more sensitive to involvement of the nondominant right hemisphere. The reproducibility of the fMRI values was lowest for the more bihemispherically represented left-TLE patients. Overall, our results further demonstrate that noninvasive fMRI measures of language-related lateralization may provide a practical and reliable alternative to invasive testing for presurgical language lateralization in patients with TLE. The high proportion (33%) of left-TLE patients showing bilateral or right hemispheric language-related lateralization suggests that there is considerable plasticity of language representation in the brains of patients with intractable TLE.

Adolescent↗

Right ventricular function: methodologic and clinical considerations in noninvasive scintigraphic assessment.

Right ventricular function plays an important role in many cardiac disorders. Changes in left ventricular function, right ventricular afterload and preload, cardiac medications and ischemia may affect right ventricular function. Radionuclide ventriculography permits quantitative assessment of regional and global function of the right ventricle. This assessment can be made at rest, during exercise or after pharmacologic interventions. The overlap between right ventricle and right atrium is a major limitation for gated scintigraphic techniques. The use of imaging with newer short-lived radionuclides may permit more accurate and reproducible assessment of right ventricular function by means of the first pass method. Further work in areas related to improvement of techniques and the impact of right ventricular function on prognosis is needed.

Animals↗

Spatial and temporal heterogeneity of depolarization and repolarization may complicate implantable cardioverter defibrillator therapy in Brugada syndrome.

INTRODUCTION: Dynamic variations in electrophysiologic phenomena inherent to the Brugada syndrome may complicate therapy with implantable cardioverter defibrillators (ICDs). METHODS AND RESULTS: Between 1997 and 1999, 3 of 7 patients with Brugada syndrome (1 man and 2 women, mean age 42 years) received an ICD. During follow-up, 2 patients experienced multiple inappropriate shocks. Simultaneously with dynamic changes in the surface ECG, endocardial ECGs revealed a dynamic decrease in the right ventricular R wave and an increase in the corresponding T wave, resulting in T wave oversensing. With ajmaline administration, these dynamic changes in endocardial signals were reproducible at different right ventricular sites, whereas left ventricular epicardial signals remained stable. Incremental AAI pacing and exercise stress testing resulted in similar changes in right ventricular endocardial signals, but normalization of the surface ECG apart from progressively increasing S waves in leads II, V5, and V6. Orciprenaline administration had no effect on ECG phenomena. After implantation of a left ventricular epicardial lead for sensing and pacing, no inappropriate tachycardia detection recurred. CONCLUSION: These findings demonstrate that, in Brugada syndrome, spontaneous or ajmaline-induced changes in the surface ECG may be paralleled by significant variations in the right ventricular endocardial electrogram that may result in ICD malfunction. Implantation of a left ventricular epicardial lead for sensing and pacing may be the ultimate successful approach in certain patients. To assure proper ICD function, ajmaline testing during ICD implantation appears to be helpful.

Adrenergic beta-Agonists↗