No abstract

Three-dimensional cytoarchitecture and types and features of muscle fibers were examined in soleus muscles from mdx mutant mice at different stages of development. In the 2-week-old mice, no abnormal muscle fibers were observed light microscopically, whereas in the 4-week-old animals, disrupted fibers were frequent in light microscopy and scanning electron microscopy. Muscle fibers fused with several short fiber branches appeared at the sixth week after birth and increased in number until the tenth week. In the 1-year-old mice, approximately ten or more muscle fibers were seen fused together. They had many complex branches forming an "anastomosing syncytial reticulum." Muscle fibers with irregular diameters and aggregations of the same type fibers were also observed. Our results demonstrated that these complex branched fibers might be formed by long term repetition of the degeneration and regeneration cycle during the development of soleus muscles, indicating that the characteristic features of muscle fibers with irregular diameters and aggregations of the same type fibers are certainly dependent on the existence of the complex branched fibers.

The quantitative analysis of haemoglobin oxygenation of contracting human muscle during weight-lifting exercise was studied noninvasively and directly using near-infrared spectroscopy. This method was developed as a three-wavelength method which confirmed the volume changes in oxygenated haemoglobin (oxy-Hb), deoxygenated haemoglobin (deoxy-Hb) and blood volume (total-Hb; Oxy-Hb+deoxy-Hb). Nine healthy adult men with various levels of training experience took part in the study. Ten repetition maximum (10 RM) one-arm curl exercise was performed by all the subjects. Results showed that at the beginning of the 10-RM exercise, rapid increases of deoxy-Hb and decreases of oxy-Hb were observed. In addition, total-Hb gradually increased during exercise. These results corresponded to the condition of arm blood flow experimentally restricted using a tourniquet in contact with the shoulder joint, and they showed the restriction of venous blood flow and an anoxic state occurring in the dynamically contracted muscle. In three sets of lifting exercise with short rest periods, these tendencies were accelerated in each set, while total-Hb volume did not return to the resting state after the third set for more than 90 s. These results would suggest that a training regimen emphasizing a moderately high load and a high number of repetitions, and a serial set with short rest periods such as usually performed by body builders, caused a relatively long-term anoxic state in the muscle.

No abstract

An experimental rat model was used to investigate the mechanisms of serum creatine phosphokinase (CPK) elevation in strangulated small bowel obstruction. Two models were used: a strangulated ileus model with the bowel lumen and blood flow obstructed simultaneously, and a control ileus model with only the bowel lumen occluded. The experiments demonstrated that CPK was released into the blood when the mesenteric blood flow was restored, and that CPK was released into the intestinal lumen in the strangulated ileus model but not the control ileus model. CPK activity in the mucosal layer of the strangulated ileus model was significantly decreased compared with that in the control ileus model. Purified CPK injected into the intestinal lumen was absorbed by the healthy intestine. These results suggest a new mechanism of serum CPK elevation in strangulated small bowel obstruction in which serum CPK is elevated with a significant decrease in mucosal CPK. Strangulated bowel content including mucosal CPK may be reabsorbed by the healthy distal intestine when bowel obstruction is incomplete.