Myosin step size: estimates from motility assays and shortening muscle.
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Actins↗
Biomedical subjects
K Burton
Publications and source records attributed to K Burton.
An improved method of stature measurement for quantitative determination of spinal loading. Application to sitting postures and whole body vibration.
A refined procedure for measuring stature is described; this provides a reproducibility error of 0.4 mm. The procedure accommodates the natural diurnal change in stature and permits estimation of the net stature change caused by a change in spinal loading. A series of measurements done with a cohort of 20 young and middle-aged persons showed that stature decrease was related linearly to the quasi-static load on the spine. The coefficient of proportionality between load and height loss was inversely proportional to the cross-sectional area of the lumbar discs. This method was used to investigate sitting postures and whole-body vibration to demonstrate the applicability of the procedure to quantify spinal strain (and, therefore, estimate comparative loading) in applied ergonomics. Sitting invariably led to an increase in stature, regardless of the type of chair used or the posture maintained. Whole-body vibration did not induce any loss of stature. Thus, this novel approach was able to enhance understanding of spinal behavior under different loading conditions.
Adult↗
Child sexual abuse and forensic psychiatry: evolving and controversial issues.
Child sexual abuse has received growing attention in recent years, and the topic continues to spark controversy among mental health and legal professionals as well as in the popular media. This paper will review the concept of child sexual abuse, cover relevant definitions, address the clinician's role, and then will address the principal evolving and controversial areas. These areas include psychic damages, false allegations, improper investigatory techniques, use of anatomical dolls, admissibility of expert testimony, hearsay testimony, and the competency of minors to testify.
Adolescent↗
Crossbridge activity monitored from the state of polarization of light diffracted by activated frog muscle fibres.
The polarization properties of the first diffraction order have been measured when single frog fibres are illuminated by laser light. The relative difference in the amplitudes of the orthogonal electric field polarization components (differential field ratio) as well as their phase shift normalized by the pathlength (birefringence) have been obtained from fibres at rest and during fixed-end twitches and tetani. The differential field ratio decreased during contraction and the change during a single twitch averaged 69% of that during a companion tetanus. The birefringence of the first order averaged 2.80 +/- 0.59 x 10(-3) (mean +/- SD) at rest and the average decrease during a tetanus was 8.4% +/- 6.4%. The decrease in the differential field ratio upon activation was a decreasing function of sarcomere length, maximum at rest length and falling to zero at about 3.7 microns. Differences between the two first diffraction orders were observed for both the differentiated field ratio and the birefringence. At the time when force had risen to half the value reached at the end of the fast rise of tension, the change in the differential field ratio lead the tension by about 10-15 ms. The differential field ratio returned to its resting value after the fall of tension. The above results suggest that the differential field ratio is a sensitive indicator of intact fibre structure. The temporal lead in the differential field ratio with respect to tension rise supports models in which crossbridges initially attach in a non-force-producing state.
Animals↗
Sarcomere length behaviour along single frog muscle fibres at different lengths during isometric tetani.
A detailed investigation of sarcomere lengthening and shortening during fixed-end tetani has been made along frog muscle fibres stretched over a large range of sarcomere lengths. A variety of sources of error common in such measurements are quantitated and give an uncertainty in sarcomere length of about 53-62 nm. The difference in sarcomere length calculated from the left and right first orders at rest was 21 nm +/- 16 nm and this is suggested to be a measure of 'Bragg artefact'. The laser diffraction measurements showed that the shortening end regions decrease in size during contraction and that the magnitude of shortening is increased at greater fibre extensions. The average length change and sarcomere length of the central and end regions was 0.10 microns (2.85 microns) and 0.37 microns (2.66 microns), respectively. The sarcomere length of the end regions at the end of creep was regularly observed to be less than 2.1 microns. An unexpected finding was the occasional observation of striations in the transition zone between lengthening and shortening regions which remained nearly isometric during a period of tension rise during creep. Measurements of diffraction order linewidth do not suggest increased sarcomere length dispersion in these areas. A smooth transition from shortening to lengthening was always observed. Although our data are in general agreement with the models proposed by Morgan, Mochon and Julian (Biophys. J. 39 (1982) 189-96) and Edman and Reggiani (J. Physiol. (Lond.) 351 (1984) 169-98), specific differences which do exist are discussed.
Animals↗
Polarization states of diffracted light. Changes accompanying fiber activation.
Measurement of the state of optical polarization of light diffracted from single, skinned and intact fibers of anterior tibialis muscle from Rana pipiens revealed a dependence upon rigor, activation, and sarcomere length (SL) change. Changes in total birefringence, delta nT, and differential field ratio value, rT, were determined. In a relaxed, skinned fiber the total birefringence value, delta nT, decreases as sarcomere length is increased from 2.1 microns to approximately 2.8-3.0 microns. From there it increases significantly to a value of approximately 1.8 x 10(-3) at a sarcomere length of 3.6 microns. The differential field ratio, rT, also shows a biphasic response to increasing sarcomere length, first exhibiting a rapid decrease over shorter SL and leveling out after the SL is beyond 3.0 microns. In comparison, relaxed intact fibers change substantially less upon sarcomere length change, showing little change in birefringence and a small bi-phasic change in rT. Skinned fibers were activated using a solution that has the same ionic strength as the relaxing solution and allows repeatable, and sustained activation. A decrease in both delta nT and rT was observed upon fiber activation. The decrease in delta nT and rT was slightly larger at shorter sarcomere lengths than at longer lengths. Relaxed fibers placed in rigor showed changes in delta nT and rT similar to those observed in activated fibers. These results are consistent with the hypothesis that, after activation, a significant portion of the thick filament cross-bridges rotate towards the actin filament resulting in redistribution of the interfilament mass content. They are also consistent with an average orientation of crossbridges in the overlap region different from that in the nonoverlap region.
Animals↗
Diagnostic criteria for intraarticular T.M. disorders.
Epidemiological investigations about the prevalence of TMJ ID and osteoarthritis have largely reported the symptoms and signs associated with these disorders without specific criteria to establish the diagnosis. In this study, specific diagnostic criteria have been developed, using historical, clinical and tomographic items that are predictive of the presence and stage of TMJ internal derangement. The diagnostic criteria were compared to arthrotomography to assess their diagnostic accuracy. Overall, the percent agreement was 75%. The predictability of specific stages of TMJ ID varied. Overall, sensitivity and specificity of the criteria were acceptable. The diagnosis of osteoarthritis was predicted only with tomography. Utilization of these diagnostic criteria in epidemiological studies is valid due to their high overall predictiveness when applied to a large population.
Adolescent↗
The case of the missing polyp. The primary care physician's dilemma.
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Barium↗
Efficacy of dopamine agonists in dystonia.
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Adult↗
The treatment of tremor.
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Adrenergic beta-Antagonists↗
Optical ellipsometry on the diffraction order of skinned fibers. pH-induced rigor effects.
The polarization properties of light diffracted from single-skinned fibers of skeletal muscles have been examined under conditions in which the bathing solution pH and the ionic strength are changed. For fibers in the relaxed state, we observe large decreases in both the total depolarization signal, r, and the total diffraction birefringence signal, delta nT, upon pH change from 7.0 to 8.0 at normal ionic strength. However, if the ionic strength is raised, then the r-value change as the pH changes from pH 7.0 to pH 8.0 is much smaller. If the rigor state is achieved at pH 8.0, and 0 mM ATP under either of the ionic strength conditions, the fiber can still be stretched. Rigor stiffness for this state is only approximately 20% that of the value of the stiffness at pH 7.0 rigor. Electron micrographs obtained under this pH 8.0 rigor state show that the overlap region can be decreased upon stretching the fiber, signifying a different kind of weaker-binding rigor state. Optically, the weaker-binding rigor state has a lower depolarization signal and larger form birefringence than the strong-binding rigor state. To convert from one type of rigor state (pH 7.0) to the other rigor state (pH 8.0), or vice versa, the fiber must first be relaxed. Apparently, either of the rigor states can block the full impact of the pH effect.
Animals↗
Lesions of the putamen: their relevance to dystonia.
Two patients with acquired dystonia were studied by computed imaging techniques and found to have lesions predominantly involving the putamen. The implications of these findings are discussed, and it is concluded that, for the genesis of dystonia, a relative increase of other inputs to the pallidum may be important, such as those from the caudate and subthalamic nuclei.
Adult↗
Light diffraction patterns and sarcomere length variation in striated muscle fibers of Limulus.
Light diffraction patterns produced by Limulus striated muscle fibers were examined. Segments of fibers were glycerinated, fixed or bathed in relaxing solution. Profiles of the intensity of a diffracted order vs. the angle of incidence of the laser beam often exhibited narrow peaks with the fiber at rest length. The incident angles at which the intensity of left and right orders is greatest are used to calculate the sarcomere length, supporting the notion that regions of the fiber are organised into Bragg reflecting planes. These profiles developed subpeaks and broadened upon stretch of the fiber. The broad angle scan profiles are suggested to result from a decrease in the regular packing of myofibrils as the fiber is lengthened. The angular width of the subpeaks is used to estimate the thickness of clusters of myofibrils. The variation in sarcomere length along the fiber, as determined by the 0th to 1st diffraction order spacing, was dependent upon the fiber preparation. Glycerinated fibers and those bathed in relaxing solution showed more variation than fixed fibers. The variation of sarcomere length is compared to the variation in thick filament lengths in Limulus reported by Dewey et al. (1982). These results are compared to those obtained from frog fiber segments.
Animals↗
Optical depolarization changes in single, skinned muscle fibers. Evidence for cross-bridge involvement.
Optical ellipsometry studies of single, skinned muscle fibers conducted on the diffraction orders have yielded spectra that are sensitive to the state of the fiber. The linearly polarized light field vector becomes elliptically polarized as it passes through the fiber and may be collected at the diffraction orders. Fibers that have been subjected to extraction of myosin (0.6 M KCl) retain a weak diffraction pattern and exhibit a substantially decreased depolarization of incident linearly polarized light. A significant decrease in polarization is seen in skinned fibers that are subject to an increase in pH from 7.0 to 8.0. This increase in pH results in a decrease of approximately 30% in the depolarization angle of single fibers. The major decrease in depolarization angle that we observe at pH 8.0 is consistent with the notion that as cross-bridges move out from the shaft of the thick filament, their ability to cause depolarization of the incident linearly polarized light decreases. This interpretation is also consistent with the work of Ueno and Harrington where the decrease in the ability to cross-link S-1 and S-2 to the thick filament at pH 8.2 suggests cross-bridge movement away from the thick filament. A large decrease in birefringence, seen after treatment of skinned fibers with alpha-chymotrypsin, appears to be related to the breakdown of myosin into rod, S-1, heavy meromyosin, and light meromyosin.
Adenosine Triphosphate↗
The computer-based anesthetic monitors: the Duke Automatic Monitoring Equipment (DAME) system and the microDAME.
From 1972 to 1983 the Duke University Department of Anesthesiology designed, built, and maintained most of its own operating room patient monitoring equipment. Construction of a new hospital facility in 1980 provided the opportunity to design and test a new computer-based system, the Duke Automatic Monitoring Equipment (DAME) System. The system consist of microcomputer-based instrumentation on monitoring carts, which communicate with a central minicomputer that allows selection of different software monitoring packages based on the needs of the patient. Multiple problems, including frequent total monitoring failures during surgery, plagued the DAME System in its first year of operation. Despite resolution of many of these problems, user acceptance was poor because of the large size and weight of the monitoring carts, the inadequate quality of displayed physiological waveforms, and inability to overcome the difficulties of the man-machine interface. Because the remaining problems could not be rectified with the existing monitoring carts, a new generation of monitors was designed. The smaller, multiprocessor microDAME was designed to be as automatic and user tolerant as possible. It would omit much of the flexibility that had proved undesirable in the DAME system. When the microDAME was nearly completed, however, departmental research in that area ceased. It remains for others to apply our experiences to further improve operating room patient monitors.
Anesthesiology↗
Depolarization spectrum of diffracted light from muscle fiber. The intrinsic anisotropy component.
The depolarization signal of the diffraction patterns from muscle fibers includes information that differs from that of transmission birefringence experiments. Although both the birefringence studies and the phase shift studies of Yeh et al. (Yeh, Y, and G. Pinsky, 1983, Biophys. J., 42:83-90; Yeh, Y., M. E. Corcoran, R. J. Baskin, and R. L. Lieber, 1983, Biophys. J., 44:343-351) include inseparable intrinsic and form contributions, the present analysis shows that the magnitude of the E-field components of diffracted light is affected only by the intrinsic contribution. We have analyzed the amplitude portion of the data of which the phase shift portion had previously been reported (Yeh, Y., M. E. Corcoran, R. J. Baskin, and R. L. Lieber, 1983, Biophys. J., 44:343-351). For the relaxed-to-rigor transition, these field amplitudes also exhibit changes when ATP concentration is decreased. The observed decrease in optical depolarization upon rigor is consistent with the idea that optically anisotropic elements move away from the myosin thick filament under such conditions.
Adenosine Triphosphate↗
Parkinson's disease: a comparison of mesulergine and bromocriptine.
Previous studies with mesulergine (CU 32-085) demonstrated safety and efficacy in short-term observations of patients with Parkinson's disease. We compared mesulergine with bromocriptine in 20 patients with Parkinson's disease. Eighteen patients completed the randomized, double-blind, crossover study. Clinical assessments employed the UBC scale and "Mini-Mental State" examination; neurophysiologic measurements were undertaken on wrist rigidity and speed and accuracy of hand movement, and toxicity screening tests were compared. There were no significant differences between the effects of mesulergine (mean dosage, 27.4 mg/d) and bromocriptine (mean dosage, 40.8 mg/d).
Adult↗
A new indirect method for measuring spinal conduction velocity in man.
A non-invasive, indirect method for measuring spinal cord mixed afferent-efferent conduction is described. The method is based upon eliciting late reflex responses labelled R1 and R2 from voluntarily contracting thenar and tibialis anterior muscles by preferentially stimulating median and common peroneal sensory nerve fibres. The mean onset latencies of R1 measured 27.5 msec and 30.6 msec recorded from hand and leg muscles respectively. R2 mean onset latencies measured 46.0 msec and 65.1 msec respectively. R1 has characteristics similar to an H-reflex. R2 is a long-loop reflex of unknown pathway assumed to involve similar circuits and rostral turn around points when elicited by both arm and leg stimulation. Mean spinal cord conduction time between the seventh cervical and fifth lumbar spinous processes, is given by (formula; see text) It measured 7.95 msec and the calculated mean conduction velocity was 57.9 +/- 5.7 m/sec.
Adult↗