Factors Underlying the Early Limb Muscle Weakness in Acute Quadriplegic Myopathy Using an Experimental ICU Porcine Model

The basic mechanisms underlying acquired generalized muscle weakness and paralysis in critically ill patients remain poorly understood and may be related to prolonged mechanical ventilation/immobilization (MV) or to other triggering factors such as sepsis, systemic corticosteroid (CS) treatment and administration of neuromuscular blocking agents (NMBA). The present study aims at exploring the relative importance of these factors by using a unique porcine model. Piglets were all exposed to MV together with different combinations of endotoxin-induced sepsis, CS and NMBA for five days. Peroneal motor nerve conduction velocity and amplitude of the compound muscle action potential (CMAP) as well as biceps femoris muscle biopsy specimens were obtained immediately after anesthesia on the first day and at the end of the 5-day experimental period. Results showed that peroneal nerve motor conduction velocity is unaffected whereas the size of the CMAP decreases independently of the type of intervention, in all groups after 5 days. Otherwise, despite a preserved size, muscle fibre specific force (maximum force normalized to cross-sectional area) decreased dramatically for animals exposed to MV in combination with CS or/and sepsis. These results suggest that the rapid declines in CMAP amplitude and in force generation capacity are triggered by independent mechanisms with significant clinical and therapeutic implications

Diaphragm Muscle Weakness in an Experimental Porcine Intensive Care Unit Model

In critically ill patients, mechanisms underlying diaphragm muscle remodeling and resultant dysfunction contributing to weaning failure remain unclear. Ventilator-induced modifications as well as sepsis and administration of pharmacological agents such as corticosteroids and neuromuscular blocking agents may be involved. Thus, the objective of the present study was to examine how sepsis, systemic corticosteroid treatment (CS) and neuromuscular blocking agent administration (NMBA) aggravate ventilator-related diaphragm cell and molecular dysfunction in the intensive care unit. Piglets were exposed to different combinations of mechanical ventilation and sedation, endotoxin-induced sepsis, CS and NMBA for five days and compared with sham-operated control animals. On day 5, diaphragm muscle fibre structure (myosin heavy chain isoform proportion, cross-sectional area and contractile protein content) did not differ from controls in any of the mechanically ventilated animals. However, a decrease in single fibre maximal force normalized to cross-sectional area (specific force) was observed in all experimental piglets. Therefore, exposure to mechanical ventilation and sedation for five days has a key negative impact on diaphragm contractile function despite a preservation of muscle structure. Post-translational modifications of contractile proteins are forwarded as one probable underlying mechanism. Unexpectedly, sepsis, CS or NMBA have no significant additive effects, suggesting that mechanical ventilation and sedation are the triggering factors leading to diaphragm weakness in the intensive care unit

Railway-induced ground vibrations – a review of vehicle effects

This paper is a review of the effect of vehicle characteristics on ground- and track borne-vibrations from railways. It combines traditional theory with modern thinking and uses a range of numerical analysis and experimental results to provide a broad analysis of the subject area. First, the effect of different train types on vibration propagation is investigated. Then, despite not being the focus of this work, numerical approaches to vibration propagation modelling within the track and soil are briefly touched upon. Next an in-depth discussion is presented related to the evolution of numerical models, with analysis of the suitability of various modelling approaches for analysing vehicle effects. The differences between quasi-static and dynamic characteristics are also discussed with insights into defects such as wheel/rail irregularities. Additionally, as an appendix, a modest database of train types are presented along with detailed information related to their physical attributes. It is hoped that this information may provide assistance to future researchers attempting to simulate railway vehicle vibrations. It is concluded that train type and the contact conditions at the wheel/rail interface can be influential in the generation of vibration. Therefore, where possible, when using numerical approach, the vehicle should be modelled in detail. Additionally, it was found that there are a wide variety of modelling approaches capable of simulating train types effects. If non-linear behaviour needs to be included in the model, then time domain simulations are preferable, however if the system can be assumed linear then frequency domain simulations are suitable due to their reduced computational demand

Survey of fish stocks on Föglö, SE Åland

In the summer of 2006 Föglö was investigated as the second survey area in the long term project of fish stock survey on Åland. Seining for juvenile fish and adult smallsized fish species were performed on Föglö and in responding areas of Geta and Eckerö. Test-fishing for larger adult fish species were performed on Föglö and in the responding areas of Finbo and Kumlinge. Seining for juvenile flounder and turbot were done across the mainland of Åland. The purpose was to investigate the status and recruitment ability of the fish stock on Föglö in comparison to reference areas. Perch was the most common species in the test-fishing and occurred frequently on all depth strata, although the recruitment of perch on Föglö seems poorer than in the reference areas. Cyprinids were also common in the test-fishing, which might indicate eutrofication. Diminishing pike populations on Föglö have previously been of great concern. The pike catches in this investigation were however no lesser than in the reference areas. In the seinings for warm water species mostly three-spined stickleback and nine-spined stickleback were caught on Föglö and three-spined stickleback and goby in the responding areas. In the seinings for flounder and turbot juveniles only few individuals were caught on Föglö in contrast to the responding areas where they were caught more frequently. Cladophora spp. was exctensively present on Föglö and probably affected negatively both perch, pike, flounder and turbot juveniles. Both the high number of perch and cyprinides and the overgrown bottoms indicate eutrofication on Föglö. Generally species of commersal interest were caught in low numbers on Föglö in the test-fishing, except for perch, and the recruitment of theese species were also poorer on Föglö than in the responding areas

Fish and crayfish stocks in five lakes in the Åland Islands in the summer of 2007

This study was carried out during the summer of 2007 in five lakes in the Åland Islands; the Lake Vargsundet, Lake Markusbölefjärden, Lake Långsjön, Lake Östra Kyrksundet and Lake Västra Kyrksundet. The aim of the study was to get information on fish and crayfish stocks in the lakes. Test fishing for crayfish was performed three times in each lake. Test fishing for fish was performed three times in the Lake Vargsundet and ones in the rest of the lakes. Seining for juvenile fish was performed twice in the Lake Vargsundet. All investigated lakes were to some extent eutrophicated and had large or very large fish stocks. The Lake Markusbölefjärden and Lake Långsjön, which are highly productive lakes, had very large fish and crayfish stocks. The crayfish stocks consisted mainly of large individuals (10–12 cm), which might indicate problems in recruitment. The Lake Östra Kyrksundet had a large crayfish stock that consisted mainly of small individuals, which might indicate intraspecific competition. The Lake Västra Kyrksundet had a normal crayfish stock and a slightly smaller fish stock than the other lakes. The Lake Vargsundet, which is a deep and meromictic lake, had a large fish stock but a small crayfish stock. Results of the seining indicate that there was recruitment of fish in the Lake Vargsundet. Annual monitoring of the crayfish stocks is recommended in all the investigated lakes. In the Lake Markusbölefjärden and Lake Långsjön we recommend a future study to verify if small crayfish exist in order to determine whether or not the crayfish populations in these lakes suffer from recruitment problems. In the Lake Östra Kyrksundet we recommend that the crayfish stock is followed up carefully in order to get verification on if the trend towards a larger stock with smaller individuals continues. Fishing for crayfish can proceed as before in the Lake Markusbölefjärden, Lake Långsjön, Lake Västra Kyrksundet and Lake Östra Kyrksundet. In the Lake Vargsundet a break in fishing for crayfish is recommended until the stock has recovered

Myosin∶actin ratios.

<p>Values for day 1 (empty colored bars) and day 5 (hatched colored bars) from mechanically ventilated/sedated/immobilized (MV group) piglets, MV together with neuromuscular blocking agents (NMBA group), MV together with corticosteroid administration (CS group), MV together an endotoxin-induced sepsis (sepsis), and MV together with sepsis, CS and NMBA (ALL group). Data are presented as means ± SEMs.</p

Animal treatment.

<p>MV (mechanical ventilation), sepsis (endotoxemia was induced by a continuous infusion of Escherichia coli endotoxin), NMBA (neuromuscular blocking agent, i.e., continuous infusion of rocuronium, 25 mg·h⁻¹), CS (corticosteroid given as bolus doses of hydrocortisone 50 mg, ×3 daily) and ALL (MV+CS+sepsis+NMBA). N: number of animals; BE: base excess; PP: peak pressure.</p

Single muscle fibre size and contractile function.

<p>Cross-sectional area (CSA), specific force (maximal force production normalized to CSA) and maximum unloaded shortening velocity (V₀). Values for day 1 (empty colored bars) and day 5 (hatched colored bars) from mechanically ventilated/sedated/immobilized (MV group) piglets, MV together with neuromuscular blocking agents (NMBA group), MV together with corticosteroid administration (CS group), MV together an endotoxin-induced sepsis (sepsis), and MV together with sepsis, CS and NMBA (ALL group). Data are presented as means ± SEMs. Asterisk denotes a statistically significant difference compared with day 1 (p<0.05).</p