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Biomedical subjects

S Lobert

Publications and source records attributed to S Lobert.

25 records · Page 2Linked to original sources
PubMed1991

Studies of crystallization conditions for native and subtilisin-cleaved pig brain tubulin.

A survey of crystallization conditions for pig brain tubulin, using standard vapor diffusion techniques in sitting drops or capillaries, has resulted in irregular, fragile needles or plates with a largest dimension of 0.5 mm. These occurred in 2.5% PEG (MW 3350), 0.1 M Pipes, pH 6.2 and 6.4, 2-16 mM MgSO4, 10-15 mM DTE, and 0.1 mM GDP at 8 degrees C. When GTP replaced GDP these aggregates did not form under any of the conditions surveyed (temperature: 8-10 degrees C; MgSO4: 2-16 mM; pH 6-7; PEG, MW 3350: 1.25-12.5%). EM observations demonstrated that sheets of rings appear in crystal solutions in the presence of GDP or GTP. These results are consistent with the results of Howard and Timasheff (1986, Biochemistry 25, 8292-8300) that tubulin rings form in the presence of GDP or GTP but more readily in GDP. Tubulin crystallization experiments are hampered by tubulin's high degree of heterogeneity. Much of the variability lies in the carboxyl terminal region. Conditions for limited digestion of the heterodimer by subtilisin, removing only the carboxyl terminus, were determined. Reduction of heterogeneity was demonstrated by isoelectric focusing. The solubilities of native and subtilisin-cleaved tubulin in MgSO4, (NH4)2SO4, PEG (MW 1450, 3350, 10,000), DMSO, and MPD were compared. Subtilisin-cleaved tubulin precipitated more readily than native tubulin under all conditions surveyed, consistent with the removal of the highly acidic carboxyl terminus. Vapor diffusion experiments using subtilisin-cleaved tubulin under conditions where native tubulin forms needles or plates resulted in similar aggregates.

Animals↗
PubMed1990

Fiber diffraction analysis of cucumber green mottle mosaic virus using limited numbers of heavy-atom derivatives.

The structure of cucumber green mottle mosaic virus has been determined from fiber diffraction data to a resolution of 5 A, using only two derivatives and without making any specific assumptions about the molecular structure of the virus. Because of the cylindrical averaging of fiber diffraction data, large numbers of heavy-atom derivatives have been required in previous structure determinations, but it is shown that simplifying assumptions about the overlapping intensities in fiber diffraction are sufficient for structure determination at this resolution using only two derivatives.

Image Processing, Computer-Assisted↗
PubMed1989

[Model studies of muscle postural control in children with spastic hemiparesis: pathophysiologic and clinical relevance].

By means of a biocybernetic method the transfer behaviour of postural motor control system was characterized in children with spastic hemiparesis and matched healthy subjects. There were significant differences between the initial reactions of the postural motor systems of both examination groups to pseudorandom torque sequences (fig. 3, tab. 1). Considering these results we created a postural motor control model for both examinations groups (model see fig. 2). From this model it is possible to estimate separately the biomechanical effect of augmented segmental reflex activity and muscle-inherent dysfunctions in patients with spastic syndrome (fig. 4). The determination of these disturbed functions enables us to give instructions on a focused treatment of spastic syndrome according to the dominant dysfunction quantified.

Brain Damage, Chronic↗
PubMedDate not supplied

Biocybernetic investigations of pursuit and posture motor control--a strategy for a detailed characterization of movement disorders in brain-damaged children.

By means of a biocybernetic approach the pursuit and posture motor control of brain-damaged children with spastic hemiparesis and disturbed motor coordination of mild extent were investigated. The postural motor control system was loaded by pseudostochastic binary torque sequences applied to the wrist. The dynamics of this system were characterized on the basis of the parameters forearm displacement as well as surface-EMG of M. Biceps and Triceps (calculations of weight functions). The pursuit motor control was analyzed by a pursuit tracking method. By this way the motor capacity for fine and rough motor coordination, motor rhythm, motor adaptation, the maximal speed of movements and motor reaction time could be tested. Considering these results a characterization of movement control on different levels of motor regulation was possible (dynamics of muscular, spinal, and supraspinal components of motor control).

Brain Damage, Chronic↗