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This paper experimentally demonstrates the feasibility of a 2 x 2 MIMO optical communication system based on mode group diversion multiplexing in the presence of strong mode crosstalk over 250m GI-MMF. The parallel signal detection and processing are realized through the use of PD array.

Previous studies with hypertriglyceridemic APOC3 transgenic mice have suggested that apolipoprotein C-III (apoC-III) may inhibit either the apoE-mediated hepatic uptake of TG-rich lipoproteins and/or the lipoprotein lipase (LPL)-mediated hydrolysis of TG. Accordingly, apoC3 knockout (apoC3(-/-)) mice are hypotriglyceridemic. In the present study, we attempted to elucidate the mechanism(s) underlying these phenomena by intercrossing apoC3(-/-) mice with apoE(-/-) mice to study the effects of apoC-III deficiency against a hyperlipidemic background. Similar to apoE(+/+) apoC3(-/-) mice, apoE(-/-)apoC3(-/-) mice exhibited a marked reduction in VLDL cholesterol and TG, indicating that the mechanism(s) by which apoC-III deficiency exerts its lipid-lowering effect act independent of apoE. On both backgrounds, apoC3(-/-) mice showed normal intestinal lipid absorption and hepatic VLDL TG secretion. However, turnover studies showed that TG-labeled emulsion particles were cleared much more rapidly in apoC3(-/-) mice, whereas the clearance of VLDL apoB, as a marker for whole particle uptake by the liver, was not affected. Furthermore, it was shown that cholesteryl oleate-labeled particles were also cleared faster in apoC3(-/-) mice. Thus the mechanisms underlying the hypolipidemia in apoC3(-/-) mice involve both a more efficient hydrolysis of VLDL TG as well as an enhanced selective clearance of VLDL cholesteryl esters from plasma. In summary, our studies of apoC3(-/-) mice support the concept that apoC-III is an effective inhibitor of VLDL TG hydrolysis and reveal a potential regulating role for apoC-III with respect to the selective uptake of cholesteryl esters.

Apolipoprotein E (apoE) is an important determinant for the uptake of triglyceride-rich lipoproteins and emulsions by the liver, but the intracellular pathway of apoE following particle internalization is poorly defined. In the present study, we investigated whether retroendocytosis is a unique feature of apoE as compared with apoB by studying the intracellular fate of very low density lipoprotein-sized apoE-containing triglyceride-rich emulsion particles and LDL after LDLr-mediated uptake. Incubation of HepG2 cells with [(3)H]cholesteryl oleate-labeled particles at 37 degrees C led to a rapid release of [(3)H]cholesterol within 30 min for both LDL and emulsion particles. In contrast, emulsion-derived (125)I-apoE was more resistant to degradation (>/=120 min) than LDL-derived (125)I-apoB (30 min). Incubation at 18 degrees C, which allows endosomal uptake but prevents lysosomal degradation, with subsequent incubation at 37 degrees C resulted in a time-dependent release of intact apoE from the cells (up to 14% of the endocytosed apoE at 4 h). The release of apoE was accelerated by the presence of protein-free emulsion (20%) or high density lipoprotein (26%). Retroendocytosis of intact particles could be excluded since little intact [(3)H]cholesteryl oleate was released (<3%). In contrast, the degradation of LDL was complete with virtually no secretion of intact apoB into the medium. The intracellular stability of apoE was also demonstrated after hepatic uptake in C57Bl/6 mice. Intravenous injection of (125)I-apoE and [(3)H]cholesteryl oleate-labeled emulsions resulted in efficient LDLr-mediated uptake of both components by the liver (45-50% of the injected dose after 20 min). At 1 h after injection, only 15-20% of the hepatic (125)I-apoE was degraded, whereas 75% of the [(3)H]cholesteryl oleate was hydrolyzed. From these data we conclude that following LDLr-mediated internalization by liver cells, apoE can escape degradation and can be resecreted. This sequence of events may allow apoE to participate in its hypothesized intracellular functions such as mediator of the post-lysosomal trafficking of lipids and very low density lipoprotein assembly.

Patients unable to perform heavy leg exercises cannot perform standard exercise ECG tests using bicycle or treadmill ergometry. A rowing ergometer was developed to enable an electrocardiographic stress test. Sixteen ambulatory patients with documented coronary insufficiency performed graded exercises. Comparison revealed no significant differences in several areas. Eleven patients with above-knee amputations, inevitable because of peripheral vascular disease, were able to perform rowing exercise only. This can result in cardiac loads adequate for diagnosis of coronary heart disease. No patient experienced difficulties with rowing. Rowing exercise can be a suitable alternative to bicycle exercise for the evaluation of coronary artery disease.

Mathematical simulation models are of growing importance in the design stage and for the operation of mooring facilities at exposed locations. In this paper such a model is described for the prediction of motions and mooring loads of ships and other floating structures moored in irregular waves, wind, and current. The mathematical model is based on the equations of motion in the time domain. This approach allow nonlinear and asymmetric mooring loads and arbitrarily in time varying excitation of the vessel. Input variables are: environmental conditions; mooring layout; elasticity characteristics of mooring lines and fenders; and geometry of the vessel. Output information includes: time histories; spectra and statistical values of motions, and mooring loads. Results are presented of an extensive validation study on the behavior of a 200,000 TDW tanker moored to an offshore jetty in shallow water. From the results it may be concluded that there is good qualitative and quantitative agreement between the results of the computer model and the experimental results.

Abstract: Various anode-cathode configurations in a nerve cuff are modelled to predict their spatial selectivity characteristics for functional nerve stimulation. A 3D volume conductor model of a monofascicular nerve is used for the computation of stimulation-induced field potentials, whereas a cable model of myelinated nerve fibre is used for the calculation of the excitation thresholds of fibres. As well as the usual configurations (monopole, bipole, longitudinal tripole, ‘steering’ anode), a transverse tripolar configuration (central cathode) is examined. It is found that the transverse tripole is the only configuration giving convex recruitment contours and therefore maximises activation selectivity for a small (cylindrical) bundle of fibres in the periphery of a monofascicular nerve trunk. As the electrode configuration is changed to achieve greater selectivity, the threshold current increases. Therefore threshold currents for fibre excitation with a transverse tripole are relatively high. Inverse recruitment is less extreme than for the other configurations. The influences of several geometrical parameters and model conductivities of the transverse tripole on selectivity and threshold current are analysed. In chronic implantation, when electrodes are encapsulated by a layer of fibrous tissue, threshold currents are low, whereas the shape of the recruitment contours in transverse tripolar stimulation does not change.

Abstract: Animal experiments and model simulations of monopolar, intrafascicular nerve stimulation are presented to study force-current relationships (recruitment curves). The conductivity of the extraneural medium is of prime importance to the resulting recruitment curves: an insulating extraneural medium generally leads to steeper curves with lower threshold currents than a well-conducting extraneural medium. Extensive statistical comparison of experimental and model results suggests the occurrence of clustering of α-motoneurons within the fascicle, manifesting itself mainly by an increased spread in threshold currents, as opposed to the situation where the fibres are distributed uniformly throughout the entire fascicle.

Apolipoprotein E*2(Arg-158 --> Cys) (APOE*2) transgenic mice were generated and compared to the previously generated apolipoprotein E*3-Leiden (APOE*3-Leiden) transgenic mice to study the variable expression of hyperlipoproteinemia associated with these two APOE variants. In the presence of the endogenous mouse Apoe gene, the expression of the APOE*3-Leiden gene resulted in slightly elevated levels of serum cholesterol as compared with control mice (2.7 +/- 0. 5 versus 2.1 +/- 0.2 mmol/liter, respectively), whereas the expression of the APOE*2(Arg-158 --> Cys) gene did not affect serum cholesterol levels, even after high/fat cholesterol feeding. The extreme cholesterol level usually found in apoE-deficient mice (Apoe-/- mice; 23.6 +/- 5.0 mmol/liter) could be rescued by introducing the APOE*3-Leiden gene (APOE*3-Leiden.Apoe-/-; 3.6 +/- 1. 5 mmol/liter), whereas the expression of the APOE*2(Arg-158 --> Cys) gene in Apoe-/- mice minimally reduced serum cholesterol levels (APOE*2.Apoe-/-; 16.6 +/- 2.9 mmol/liter). In vivo very low density lipoprotein (VLDL) turnover studies revealed that APOE*2.Apoe-/- VLDL and APOE*3-Leiden.Apoe-/- VLDL display strongly reduced fractional catabolic rates as compared with control mouse VLDL (4.0 and 6.1 versus 22.1 pools/h). In vitro low density lipoprotein (LDL) receptor binding studies using HepG2 and J774 cells showed that APOE*2. Apoe-/- VLDL is completely defective in binding to the LDL receptor, whereas APOE*3-Leiden.Apoe-/- VLDL still displayed a considerable binding activity to the LDL receptor. After transfection of APOE*2.Apoe-/- and APOE*3-Leiden.Apoe-/- mice with adenovirus carrying the gene for the receptor-associated protein (AdCMV-RAP), serum lipid levels strongly increased (15.3 to 42.8 and 1.4 to 15.3 mmol/liter for cholesterol and 5.0 to 35.7 and 0.3 to 20. 7 mmol/liter for triglycerides, respectively). This indicates that RAP-sensitive receptors, possibly the LDL receptor-related protein (LRP), mediate the plasma clearance of both APOE*2.Apoe-/- and APOE*3-Leiden. Apoe-/- VLDL. We conclude that in vivo the APOE*2 variant is completely defective in LDL receptor binding but not in binding to LRP, whereas for the APOE*3-Leiden mutant both LRP and LDL receptor binding activity are only mildly affected. As a consequence of this difference, APOE*2.Apoe-/- develop more severe hypercholesterolemia than APOE*3-Leiden.Apoe-/- mice.

Abstract: The influence of changes in electrical conductivity, due to the muscle boundary, layers and compartments of intramuscular connective tissue and blood vessels, on computed single-muscle fibre action potentials (SFAPs) in rat hindleg muscle is calculated. The position of the active fibre is varied throughout the muscle. For fibres close to the muscle boundary, peak-to-peak voltages of SFAPs increase by up to a factor of 3 compared with the unbounded situation. For inner fibres, the presence of nearby connective tissue compartments causes an increase of up to 40%. A blood vessel in the neighbourhood of the active fibre leads to a decrease of at most 20%, for recording sites between the active fibre and the blood vessel. For recording sites beyond the blood vessel, peak-to-peak voltages increase by up to 20%.

Abstract: The relationship between nerve stimulation, pulse amplitude and isometric muscle force was measured to investigate recruitment of motor units. Force addition experiments were performed to obtain insight in the intersection of motor unit groups recruited by different electrodes. Intrafascicular and extraneural multielectrode configurations were used for nerve stimulation. Experiments were performed on rats. The common peroneal nerve was stimulated and the forces of the tibial anterior and extensor digitorum longus muscles were measured isometrically. Recruitment was more stable for intrafascicular electrodes than for extraneural electrodes. Especially for intrafascicular electrodes no strict inverse recruitment was observed. Force addition experiments indicated that small overlap of recruited motor unit groups occurred more often for intrafascicular than for extraneural electrodes.

Abstract: A microscopic model of volume conduction was applied to examine the sensitivity of the single muscle fibre action potential to variations in parameters of the source and of the volume conductor, such as conduction velocity, intracellular conductivity and intracellular volume fraction. The model results show that the sensitivity to the intracellular and extracellular conductivity depends on the distance from the source. The action potential amplitude is strongly influenced by the intracellular volume fraction. In this frequency-dependent model the amplitude is influenced by the conduction velocity to a smaller degree than predicted by previous studies, which use a noncapacitive homogeneous volume conductor model.

Abstract: Extracellular action potentials of a single active muscle fibre in a surrounding of passive muscle tissue were calculated, using a microscopic volume conductor model which accounts for the travelling aspect of the source, the structure of skeletal muscle tissue and the electrical properties at the level of single muscle fibres. Owing to the capacitive properties of the muscle fibre membranes this inhomogeneous model is frequency dependent. The results of these calculations were compared with results obtained with a macroscopic homogeneous, frequency-independent version of the model. Close to the excited fibre the extracellular action potentials of both descriptions differ in their sensitivity to variations in the intra- and extracellular conductivities. It is demonstrated that within about 300 μm the muscle fibre membrane influences the amplitude as well as the timing of the peaks of the extracellular action potential. Both volume conduction descriptions result in almost the same single-fibre action potential at large radial distances from the excited fibre. These model results are of primary interest for the quantitative interpretation of single-fibre electromyograms recorded close to an active fibre, as for example in clinical fibre-density measurements.

Abstract: The relative influences of several model parameters and measurement setups on the MEG are studied quantitatively. The influences of the number of grid points of the flux transformer and the accuracy of the measurements are analysed using as criterion a relative difference measure (RDM). In a similar way, using the RDM, the influence of various models is evaluated. The volume conductor, i.e. the head, is described by three different compartment models: the first model consists of concentric spheres, the second of eccentric spheres optimally fitting the individual compartments of the head, and the third consists of realistically shaped compartments. The evaluation of the influence of the model of the source on the MEG is studied by taking either one single current dipole or a set of two current dipoles. The RDM described in the paper is shown to be a valuable measure in the quantitative analysis of MEGs.

Without Abstract:

Abstract: Recent experiments carried out in our laboratory with the four-electrode method showed that the electrical conductivity of skeletal muscle tissue depends on the frequency of the injected current and the distance between the current electrodes. A model is proposed in order to study these effects. The model takes into account the structure of the tissue on the scale of individual fibres. It discerns three main components with respect to electrical properties: (a) extracellular medium with electrical conductivity σe; (b) intracellular medium with electrical conductivity σi; (c) muscle fibre membrane with impedance Zm. The model results show an apparent frequency dependence of the electrical conductivity of skeletal muscle tissue, as well as the way the conductivity is affected by the length the current is conducted.

The cases of 80 patients with necrosis of the femoral head who underwent operative treatment in the period April 1980 to April 1988 are reported. Altogether, 102 operative procedures were carried out: 48 intertrochanteric osteotomies, 50 arthroplasties, 3 subchrondral bone graftings, and in one case drilling of the necrotic focus. Joint-preserving methods in advanced-stage disease seem to be of doubtful use when judged by clinical and socio-economic criteria over a mean follow-up time of 4.5 years. Since no conservative treatment exists, an improvement in therapeutic results can only be achieved by early diagnosis using magnetic resonance imaging and operating when the disease is still at an early stage.