Marina Nikolić

Fibre type composition of the human psoas major muscle with regard to the level of its origin

The aim of our study was to explore the fibre type composition of the human psoas major muscle at different levels of its origin, from the first lumbar to the fourth lumbar vertebra, and to compare the muscle fibre size and distribution of different fibre types between levels with respect to its complex postural and dynamic function. Muscle samples were collected from 15 young males (younger than 35 years). Serial transverse sections (5 μm) of the samples were cut by cryomicrotome. Type I, IIA and IIX muscle fibres were typed using myosin heavy chain identification. The serial sections were analysed using a light microscope with a magnitude of 100×. The differences between measurements were evaluated using a repeated‐measures anova and Scheffé test for post‐hoc analysis. Our study showed that the human psoas major muscle was composed of type I, IIA and IIX muscle fibres. It had a predominance of type IIA muscle fibres, whereas type I muscle fibres had the largest cross‐sectional area. Type IIX muscle fibres were present as a far smaller percentage and had the smallest cross‐sectional area. Moreover, the fibre type composition of the psoas major muscle was different between levels of its origin starting from the first lumbar to the fourth lumbar vertebra. We conclude that the fibre type composition of the psoas major muscle indicated its dynamic and postural functions, which supports the fact that it is the main flexor of the hip joint (dynamic function) and stabilizer of the lumbar spine, sacroiliac and hip joints (postural function). The cranial part of the psoas major muscle has a primarily postural role, whereas the caudal part of the muscle has a dynamic role.

Effect of salbutamol on innervated and denervated rat soleus muscle

The objective of the present investigation was to perform a 14-day time-course study of treatment with salbutamol, a beta2 adrenoceptor agonist, on rat soleus muscle in order to assess fiber type selectivity in the hypertrophic response and fiber type composition. Male Wistar rats were divided into four groups: control (N = 10), treated with salbutamol (N = 30), denervated (N = 30), and treated with salbutamol after denervation (N = 30). Salbutamol was injected intraperitoneally in the rats of the 2nd and 4th groups at a concentration of 0.3 mg/kg twice a day for 2 weeks. The muscles were denervated using the crush method with pean. The animals were sacrificed 3, 6, 9, 12, and 14 days after treatment. Frozen cross-sections of soleus muscle were stained for myosin ATPase, pH 9.4. Cross-sectional area and percent of muscle fibers were analyzed morphometrically by computerized image analysis. Treatment with salbutamol induced hypertrophy of all fiber types and a higher percentage of type II fibers (21%) in the healthy rat soleus muscle. Denervation caused marked atrophy of all fibers and conversion from type I to type II muscle fibers. Denervated muscles treated with salbutamol showed a significantly larger cross-sectional area of type I muscle fibers, 28.2% compared to the denervated untreated muscle. Moreover, the number of type I fibers was increased. These results indicate that administration of salbutamol is able to induce changes in cross-sectional area and fiber type distribution in the early phase of treatment. Since denervation-induced atrophy and conversion from type I to type II fibers were improved by salbutamol treatment we propose that salbutamol, like other beta2 adrenoceptor agonists, may have a therapeutic potential in improving the condition of skeletal muscle after denervation.

Reg IV protein and mRNA expression in different rat organs.

The Reg IV gene has been documented in the human colon, small intestine, stomach and pancreas. Expression of the Reg IV in different cell types has been associated with regeneration, cell growth and cell survival, cell adhesion and resistance to apoptosis. Since the distribution of the Reg IV protein in normal rat tissues is unknown, the aim of this study was to reveal the expression of the Reg IV protein in structurally and functionally different rat organs. The expression of Reg IV gene was analyzed by Western blot and reverse transcription-polymerase chain reaction. Immunohistochemistry was used to localize Reg IV protein. Reg IV protein was expressed in pancreas, stomach, small intestine, colon, brain, spleen, kidney and urinary bladder in two-month-old male Wistar rats. In addition, the expression of Reg IV mRNA by reverse transcription-polymerase chain reaction was confirmed. Our study provides detailed information about the expression and localization of Reg IV protein in different rat organs. These findings provide an evidence of Reg IV expression in different rat organs, which may help elucidate a potential role in growth and proliferation of different cells like other members of the Reg family genes which act as growth factors in the different organs.