The program joins two research groups: 'Skeletal muscle: its structure and function'and 'Human muscle under the in vitro conditions'. The program proposed by group A is dealing with the morphological, morphometric and immunohistochemical analysis of normal and diseased muscles. It consists of three research directions: I. Morphological and histochemical characteristics of skeletal muscles: We shall continue investigating the morphology and the expression pattern of myosin heavy chain isoforms (MyHC) and their transcripts in skeletal muscles of bigger mammals. Human extraocular muscles will be analysed in different age periods to prove that human EOM do not age. Special emphasis will be given to the capillary density per muscle fibre. II. Molecular mechanisms underlying the acute myopathic changes, accompanying critical conditions. Recent investigations revealed active role of the skeletal muscle fibre in the signalling processes, triggered by different types of cytokines under the stress conditions like septic shock. In our preliminary studies we demonstrated release of IL-6 from the cultured human skeletal muscle fibre after the treatments with TNF-a. These investigation will be continued in this part of the program. III. Molecular mechanisms responsible for the insulin resistance in the human skeletal muscle fibre. Insulin resistance is the major cause of hyperglycemia in type 2 diabetics and is therefore intensively investigated. The experimental model of the in vitro innervated human muscle allows studies of the molecular mechanisms underlying insulin-induced exocytosis, which is impaired in the insulin-resistant muscle fibres. In collaboration with the research group at the Institute of Pathophysiology, which is fully equipped to follow the processes of exocytosis, we shall investigate molecular mechanisms underlying the insulin-induced translocation of the glucose transporters 4 (GLUT4) bearing vesicles to the II. Plasticity of skeletal muscle in physiological, experimental and pathological conditions Plasticity of skeletal muscles that has been thoroughly studied in our previous research will further be investigated either on experimental models, like heterochronous isotransplantation, heterotopic transplantation of the rat slow and fast muscles as well as axotonotomy and axonotmesis. Additionally, plasticity will be studied in human muscles in inactivity and in the critical illness myopathy. Special attention will be paid to the influence of the changed innervation, chorticosteroid and thyroid hormones on the expression of the myosin heavy chain isoforms and their transcripts as well as to the myogenic factors and to the changed capillary supply. A part of our research will be devoted to the investigation of the biophysical characteristics of normal and dystrophic muscles and to the morphometric analysis of the muscles in patients with the myotonic dystrophy III Epidemiology of the limb-girdle muscular dystrophy We shall continue to study the epidemiology of the 'limb-girdle dystrophy' in Slovenia. The research program proposed by group B is focused on the molecular mechanisms underlying various aspects of the development and function of the human skeletal muscle fibre. In most studies we will employ the in vitro system in which human muscle fibre is innervated by the motor neuron extending from the explant of the embryonic rat spinal cord. The main research directions will be the following: I. Molecular mechanism regulating synaptogenesis and function of the neuromuscular junction (NMJ) By "gene silencing" we will investigate the roles and expression of specific proteins participating in the formation and maintenance of the NMJ. This part of our research will be focused on agrin, AChE and BuChE, which are all important, basal lamina bound constituents of the NMJ. This part of our program includes continuation of our previous research on the structure - function relationship of the AC