Modelling of medical magnetic-resonance-imaging signals

Estimation of images of metabolite concentrations in humans from in vivo magnetic-resonance signals is considered. A 3-dimensional model function is set up in which one dimension pertains to the time domain, and the other two to the reciprocal spatial domain. In the various stages of the estimation fast Fourier transforms and a state-space approach are applied. The computation time can be limited by correcting magnetic-field inhomogeneity and classifying the various parts of the image with the aid of artificial neural networks. In difficult cases spectroscopic prior knowledge is invoked in conjunction with nonlinear least-squares fitting     

Access to the cavernous sinus through the vertebral artery: technical case report

The cavernous sinus in 3 of a series of 147 fast-flow direct carotid-cavernous fistulae was best reached through the vertebral artery. All three patients were anatomically cured without morbidity.     

The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but preceded the start of motor programming.     

On the inhibition of cholinesterases by pancuronium (author''s transl)

1. The inhibition by pancuronium of acetylcholinesterase (AChE) and of plasma cholinesterase (ChE) was investigated in vitro regarding a) the sensitivity of both enzymes; b) the mechanism and constants of inhibition; and c) the relationship between the neuromuscular blocking and the anticholinesterase activity of pancuronium. 2. Pancuronium is a reversible inhibitor of both AChE and ChE. The inhibitory potency regarding ChE ([I]50=2.7 X 10(-7) M; Ki=4.2 X 10(-8) M) is highly selective and about 1000-fold higher than compared to AChE ([I]50=2.4 X 10(-4) M; Ki=3.5 X 10(-5) M). 3. The kinetic analysis by means of an Lineweaver-Burk plot and an Arunlakshana-Schild plot displayed a pure competitive mechanism of inhibition. 4. The inhibition of AChE and ChE is thought to be induced by a reversible binding of pancuronium to the anionic subsite of the active center, thus decreasing the formation of the primary enzyme-substrate complex. 5. The clinical administration of pancuronium for muscular relaxation during anaesthesia (0.01-0.08 mg/kg) will result in a concentration of approximately 10(-7)=10(-6) M in the extracellular fluid. Thus, an inhibition of plasma ChE can be expected to occur under clinical conditions, however, probably without practical significance.     

Surgery for rupture of extensor tendons in rheumatoid arthritis

Forty-two patients underwent fifty-four operations for rupture of extensor tendons in rheumatoid disease. The results are analysed and factors affecting the results discussed.