This study characterized histochemically three fast fiber types (IIB, ID, IIA) in skeletal muscles of mouse, rat, and rabbit, with special reference to fiber types IIB and IID. The results are complemented by biochemical analyses of myosin heavy chain composition in these muscles. Fiber type delineation is based on various methods for mATPase staining with preincubations and assays under different conditions. In rat and mouse, IIB and IID fibers can be best distinguished according to their different mATPase stabilities towards formaldehyde and alkaline pH. In rabbit, the method of Matoba and Gollnick using acid pre-incubation provided best and most reproducible results. In addition to their different mATPase stabilities, the three fast fiber types M e r with regard to their oxidative capacities and aoss-sectional fiber areas in the three species. In general, Type IIB fibers are the largest and least oxidative, Type IIA fibers the smallest and most oxidative, and Type IID fibers intermediate. In rabbit, Type IID fibers are the predominant fast fiber popdation in extensor digitorum longus, psoas, and tibialis anterior muscles. As judged from histochemistry, these muscles of rabbit do not contain pure Type IIB fibers. This is in accordance with biochemical results that show the HCIId to form the majority of the myosin heavy chain complement expressed in these muscles.On the other hand, IIB fibers are numerous in rabbit adductor magnus, gastrocnemius, and vastus lateralis muscles. Similarly, appreciable amounts of myosin heavy chai n HCIII, are found in the three latter muscles of rabbit.

The myosin heavy chain (HC) composition of various rabbit muscles was analysed at both the mRNA and the protein level. S1-nuclease mapping was performed with a cDNA probe specific for myosin HCIIa, yielding a fully protected sequence for HCIIa, a partially protected sequence for HCIIb, and an additional signal putatively assigned to HCIId. At the protein level, three fast myosin HC isoforms, HCIIa, HCIIb and HCIId, were separated by gradient PAGE. The results obtained at the protein level were in agreement with the findings at the mRNA level. The expression of appreciable amounts of myosin HCIIb, the predominating isoform of fast-twitch muscles in rat and mouse, was restricted in the rabbit to only a few muscles, i.e. adductor magnus, gastrocnemius, latissimus dorsi and vastus lateralis. Typical fast-twitch muscles such as extensor digitorum longus, tibialis anterior and psoas contained only minute amounts of HCIIb. The HCIId isoform, demonstrated in the present study for the fist time in rabbit, is the predominating fast myosin HC isoform in this species. Electrophoretic analyses of myosin HC in histochemically defined single fibers confiied the lack of fibers expressing only HCIIb in tibialis anterior, whereas such fibers were found in the adductor rnagnus. In addition to fiber types IIB, IID, and IIA expressing HCIIb, HCIId, and HCIIa, respectively, an appreciable amount of hybrid fibers coexpressing two HC isoforms at various ratios were found: HCIIb > HCIId; HCIId > HCIIb; HCIId > HCIIa; HCIIa > HCIId; HCIIa > HCI; HCI > HCIIa. This fiber-type spectrum indicates possible fiber-type transitions in the order IIB t)A third fast myosin heavy chain (HC) isofom has been demonstrated in rat limb musculature by two laboratories [l -51 (for review see [6]), termed HC2x by Schiaffho et al. [l] and, because of its abundance in rat diaphragm, HCIId by Biir and Pette [4]. Assuming that HC2x and HCIId are the same, this brings the total number of fast myosin HC isoforms in rat limb musculature to three, i.e. HCIIa, HCIIb and HCIId/HC2x. Subsequent studies have revealed the presence of HCIId also in mouse [7-91 and guinea pig [8]. In light of the fact that numerous data have accumulated on the physiological and biochemical properties of rabbit muscle, it was of interest to search for the possible presence and distribution of this new isoform also in this species.In the present investigation, the myosin HC isoforms were studied at the mRNA and protein levels of wholemuscle extracts combined with protein analysis in single fibers. The presence of different myosin HC mRNA isoforms was studied by S1-nuclease mapping using a cDNA probe specific for fast myosin HC mRNA isoforms HCHa and HCIIb. At the protein level, the fast myosin HC composition was assessed by the use of an improved electrophoretic technique [5]. By combining these methods, it has become clear that HCIId, and not HCIIb, is the predominant fast isoform in rabbit fast-twitch muscles. The same conclusion has been drawn from an independent histochemical study com...

BackgroundRepresentative population-based data on the epidemiology of bronchiectasis in Europe are limited. The aim of the present study was to investigate the current burden and the trends of bronchiectasis-associated hospitalizations and associated conditions in Germany in order to inform focused patient care and to facilitate the allocation of healthcare resources.MethodsThe nationwide diagnosis-related groups hospital statistics for the years 2005–2011 were used in order to identify hospitalizations with bronchiectasis as any hospital discharge diagnosis according to the International Classification of Diseases, 10th revision, code J47, (acquired) bronchiectasis. Poisson log-linear regression analysis was used to assess the significance of trends. In addition, the overall length of hospital stay (LOS) and the in-hospital mortality in comparison to the nationwide overall mortality due to bronchiectasis as the primary diagnosis was assessed.ResultsOverall, 61,838 records with bronchiectasis were extracted from more than 125 million hospitalizations. The average annual age-adjusted rate for bronchiectasis as any diagnosis was 9.4 hospitalizations per 100,000 population. Hospitalization rates increased significantly during the study period, with the highest rate of 39.4 hospitalizations per 100,000 population among men aged 75–84 years and the most pronounced average annual increases among females. Besides numerous bronchiectasis-associated conditions, chronic obstructive pulmonary disease (COPD) was most frequently found in up to 39.2% of hospitalizations with bronchiectasis as the primary diagnosis. The mean LOS was comparable to that for COPD. Overall, only 40% of bronchiectasis-associated deaths occurred inside the hospital.ConclusionsThe present study provides evidence of a changing epidemiology and a steadily increasing prevalence of bronchiectasis-associated hospitalizations. Moreover, it confirms the diversity of bronchiectasis-associated conditions and the possible association between bronchiectasis and COPD. As the major burden of disease may be managed out-of-hospital, prospective patient registries are needed to establish the exact prevalence of bronchiectasis according to the specific underlying condition.

Denervated soleus muscles of euthyroid and hyperthyroid rats were exposed to phasic high-frequency stimulation for periods of up to 40 days and analysed for their myosin heavy chain (MHC) composition. Denervation alone induced appreciable amounts of the fast MHCIId/x and minute amounts of MHCIIb. However, the effects of phasic high-frequency stimulation exceeded by far those of denervation, leading to marked increases of these two isoforms, as well as to pronounced decreases in slow MHCI. In addition, the present study suggested a greater impact of neural activity on myosin expression than thyroid hormone.

The present article attempts to combine existing information on the distribution of fast and slow myosin isoforms in histochemically distinct muscle fibres. Four myosin heavy chain (MHC) isoforms, MHCI, MHCIIa, MHCIIb, and MHCIId(x), have been identified in small mammals and have been assigned to the histochemically defined fibre types I, IIA, IIB, and IID(X), respectively. These fibres express only one MHC isoform and are called pure fibre types. Hybrid fibres expressing two MHC isoforms are regarded as transitory between respective pure fibre types. The existence of pure and hybrid fibres even in normal muscles under steady state conditions creates a spectrum of fibre types. The multiplicity of fibre types is even greater when myosin light chains are taken into account. A large number of isomyosins results from the combinatorial patterns of various myosin light and heavy chains isoforms, further increasing the diversity of muscle fibres. As shown by comparative studies, the distribution of different fibre types varies in a muscle-specific, as well as a species-specific manner.