A Comparative Study of the Myosin Light Chain Kinases from Myoblast and Muscle Sources. Studies on the Kinases from Proliferative Rat Myoblasts in Culture, Rat Thigh muscle, and Rabbit Skeletal Muscle

Myosin light chain kinases have been isolated from rat thigh and rabbit skeletal muscle and cultured rat myoblasts. From these preparations, two types of kinases can be distinguished: calcium-dependent and calcium-independent. Both types of kinases can phosphorylate isolated P-light chains of myosin from several sources (skeletal muscle, cardiac muscle, and platelet). Data are shown which support the phosphorylation of the same site on the non-muscle P-light chains by both types of kinases. The rates of these reactions are, however, different for the two types of kinases. Kinetic analysis of the myoblast kinase show differing affinities for various P-light chains (non-muscle \u3e cardiac \u3e skeletal). In the proliferative rat myoblast, phosphorylation of myosin is a prerequisite for actin activation of the myosin ATPase activity

Discontinuity Detection for Analysis of Telerobot Trajectories

To identify spatial and temporal discontinuities in telerobot movement in order to describe the shift in operators control and error correction strategies from continuous control to move-and-wait strategies. This shift was studied under conditions of simulated increasingly time-delayed teleoperation. The ultimate goal is to determine if the time delay associated with the shift is invariant with independently imposed control difficulty. We expect this shift to manifest itself as changes in the number of discontinuity of movement path. We proposed an approach to spatial and temporal discontinuity detection algorithm for analysis of teleoperated trajectory in three dimensional space. The algorithm provides a simple and potentially objective method for detecting the discontinuity during telerobot operation and evaluating the difficulty of rotational coordinate condition in teleoperation

Visual Stability of Objects and Environments Viewed through Head-Mounted Displays

Virtual Environments (aka Virtual Reality) is again catching the public imagination and a number of startups (e.g. Oculus) and even not-so-startup companies (e.g. Microsoft) are trying to develop display systems to capitalize on this renewed interest. All acknowledge that this time they will get it right by providing the required dynamic fidelity, visual quality, and interesting content for the concept of VR to take off and change the world in ways it failed to do so in past incarnations. Some of the surprisingly long historical background of the technology that the form of direct simulation that underlies virtual environment and augmented reality displays will be briefly reviewed. An example of a mid 1990's augmented reality display system with good dynamic performance from our lab will be used to illustrate some of the underlying phenomena and technology concerning visual stability of virtual environments and objects during movement. In conclusion some idealized performance characteristics for a reference system will be proposed. Interestingly, many systems more or less on the market now may actually meet many of these proposed technical requirements. This observation leads to the conclusion that the current success of the IT firms trying to commercialize the technology will depend on the hidden costs of using the systems as well as the development of interesting and compelling content

Kinematic/Dynamic Characteristics for Visual and Kinesthetic Virtual Environments

Work was carried out on two topics of principal importance to current progress in virtual environment research at NASA Ames and elsewhere. The first topic was directed at maximizing the temporal dynamic response of visually presented Virtual Environments (VEs) through reorganization and optimization of system hardware and software. The final results of this portion of the work was a VE system in the Advanced Display and Spatial Perception Laboratory at NASA Ames capable of updating at 60 Hz (the maximum hardware refresh rate) with latencies approaching 30 msec. In the course of achieving this system performance, specialized hardware and software tools for measurement of VE latency and analytic models correlating update rate and latency for different system configurations were developed. The second area of activity was the preliminary development and analysis of a novel kinematic architecture for three Degree Of Freedom (DOF) haptic interfaces--devices that provide force feedback for manipulative interaction with virtual and remote environments. An invention disclosure was filed on this work and a patent application is being pursued by NASA Ames. Activities in these two areas are expanded upon below

Misalignment Effect Function Measurement for Oblique Rotation Axes: Counterintuitive Predictions and Theoretical Extensions

The Misalignment Effect Function (MEF) describes the decrement in manual performance associated with a rotation between operators' visual display frame of reference and that of their manual control. It now has been empirically determined for rotation axes oblique to canonical body axes and is compared with the MEF previously measured for rotations about canonical axes. A targeting rule, called the Secant Rule, based on these earlier measurements is derived from a hypothetical process and shown to describe some of the data from three previous experiments. It explains the motion trajectories determined for rotations less than 65deg in purely kinematic terms without the need to appeal to a mental rotation process. Further analysis of this rule in three dimensions applied to oblique rotation axes leads to a somewhat surprising expectation that the difficulty posed by rotational misalignment should get harder as the required movement is shorter. This prediction is confirmed. Geometry underlying this rule also suggests analytic extensions for predicting more generally the difficulty of making movements in arbitrary directions subject to arbitrary misalignments

Sexual dysfunction in the male patient with uremia: A reappraisal

Sexual dysfunction in the male patient with uremia: A reappraisal. Partial or complete impotence is common in uremia. It is not clear whether the impotence is organic or psychogenic in nature and whether uremia itself or the state of chronic illness is responsible for it. We examined these questions, by psychiatric interviews and nocturnal penile tumescence (NPT), in 50 normal subjects, 48 patients with chronic uremia, including 23 patients treated with maintenance dialysis, and 22 patients with chronic illness and normal renal function. About 40 to 50% of patients with uremia, but not those with chronic illness and normal renal function, complained of erectile dysfunction and reported a significant decrease in frequency of intercourse. There were no significant differences between patients with uremia prior to initiation of therapy and those treated with maintenance hemodialysis. NPT declines after 40 years of age. In all age groups, NPT was significantly (P < 0.01) lower in uremics than in normals or those with chronic illness. There was no correlation between erectile complaints, frequency of intercourse or NPT, and the presence or absence of depression. The frequency of intercourse correlated significantly (r = 0.68, P < 0.01) with NPT in patients with uremia. Data indicate that 50% of male patients with uremia have partial or complete impotence, which is most probably organic in nature and is related to uremia or its metabolic or hormonal consequences rather than to the state of chronic illness.Disfonctionnement sexuel chez le malade urémique de sexe masculin: Une réévaluation. L'impuissance partielle ou totale est fréquente au cours de l'urémie. La nature organique ou psychogénique de l'impuissance n'est pas claire et il n'est pas non plus établi si l'urémie par elle même ou la maladie chronique en sont responsables. Nous avons étudié ces prodromes chez 50 sujets normaux, 48 malades atteints d'urémie chronique, parmi lesquels 23 étaient traités par hémodialyse itérative., et 22 malades atteints d'affections chroniques, mais avec des fonctions rénales normales au moyen des interrogatoires psychiatriques et des érections nocturnes. Quarante à cinquante pour cent des malades urémiques, mais non pas ceux atteints de maladies chroniques avec des fonctions rénales normales, se sont plaint d'anomalies de l'érection et d'une diminution significative de la fréquence des rapports sexuels. Il n'a pas été observé de différence significative entre les malades urémiques non traitées et ceux soumis à l'hémodialyse. Les érections nocturnes dominent à partir de 40 ans. Dans tous les groupes d'age les érections nocturnes sont significativement (P < 0,01) moins fréquentes chez les urémiques que chez les sujets normaux ou les sujets atteints d'autres maladies chroniques. Il n'a pas été observé de corrélation entre la fréquence des rapports sexuels ou les érections nocturnes et la présence ou l'absence de dépression. La fréquence des rapports est significativement corrélée (r = 0,68; P < 0,01) à celle des érections nocturnes chez les sujets urémiques. Les résultats indiquent que 50% des malades urémiques males ont une impuissance partielle ou totale qui est très probablement d'origine organique et liée à l'urémie ou à ses conséquences métaboliques ou hormonales plutôt qu'à l'état de maladie chronique

Three Dimensional Tracking in Augmented Environments: User Performance Trade-Offs Between System Latency and Update Rate

Three-dimensional tracking performance was measured as a function of system latency (35-335 msec) and update rate (10-30 Hz). Twelve subjects used a custom, see-through head mounted stereo display to control the position of a virtual response cursor with hand and body movements. User performance trade-offs between latency and update rate were measured with objective and subjective measures and a possible performance model was evaluated. The results indicate that earlier findings suggesting that latency influenced tracking performance more than did update rate, could be due to previous studies having tested latency over a larger dynamic range. Iso-performance contours are used to compare objective performance with subjective perception and performance judgments