Extreme endurance training and fiber type adaptation in rat diaphragm

Abstract

Extreme endurance training was used to investigate the adaptability of the rat diaphragm muscle fibers. During the final phase of the 14-wk training program, the animals were running for 240 min/day at an estimated requirement of 80% of pretraining maximal O2 consumption. Analysis of a sample of the costal diaphragm indicated that training resulted in a 34% reduction (P less than 0.05) in the percent distribution of type IIa fibers [27.7 +/- 1.1 vs. 18.3 +/- 2.6 (SE)] and a 15% increase (P less than 0.05) in the percent of type IIb fibers (40.0 +/- 1.2 vs. 46.1 +/- 2.4). No change (P greater than 0.05) was found in the distribution of the type I fibers (32.3 +/- 1.2 vs. 35.7 +/- 1.3). Oxidative potential as assessed with NADH-tetrazolium reductase and measured microphotometrically increased (P less than 0.05) by 19% in type I fibers but did not change in either the type IIa or type IIb fibers. No effect of training was found when a different oxidative marker, succinic dehydrogenase, was employed. Similarly glycolytic potential based on the activity of alpha-glycerophosphate dehydrogenase was not affected by training. Glycogen concentration was elevated by 60% (P less than 0.01) in type I fibers and 77% (P less than 0.01) in type IIb fibers with training but was not altered (P greater than 0.05) in type IIa fibers. Reductions (P less than 0.05) in fiber area ranging from 11 to 20% were observed in all fiber types as a result of training, whereas the number of capillaries per fiber remained static.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological, histochemical, and myosin isoform analysis of the diaphragm of adult horses, Equus caballus

“…Other animals which demonstrate type IIB fibers in limb muscles have also demonstrated them in the diaphragm (Reid et al 1987;Gordon et al, 1989;Green et al, 1984) The type I predominance of the equine dia- phragm is consistent with the hypothesized requirements of fatigue resistance and continual activity required for respiration in any mammal and is particularly important for a n endurance athlete such as the horse (Peters, 1989). In addition, the horse has relatively more type I fibers than did the smaller mammals (rat: Green et al, 1989;cats: Sieck et al, 1983;dogs: Reid et al, 1987).…”

“…Vomiting is rare in the adult horse, and when seen, is related to very high gastric pressures. Often, vomiting is associated with the terminal stages of gastric dilatation (Smith, 1989). The histochemical features of the hiatal region of the diaphragm suggest it may contribute to this very strong sphincter function and inhibit emesis.…”

Formaldehyde-Induced Damage in Lungs and Effects of Caffeic Acid Phenethyl Ester: A Light Microscopic Study

“…The reduced resistance to upper and lower respiratory tract infections of workers occupationally exposed to formaldehyde could suggest changes in the function of polymorphonuclear neutrophils, which are known to be the first line of defence against bacterial infections (16). Reactive oxygen species (ROS) are formed continuously in cells as a consequence of external factors and they become harmful when they are produced in excess under abnormal conditions such as inflammation (17,18). ROS may cause cell damage and are involved in the pathophysiology of inflammation, cancer and ethanol intoxication (19,20,21).…”

Differential apoptosis-related protein expression, mitochondrial properties, proteolytic enzyme activity, and DNA fragmentation between skeletal muscles

“…For all histochemical, immunohistochemical, and immunofluorescence analyses, frozen skeletal muscle samples embedded in OCT compound were cut into 10-m serial cross sections with a cryostat (Thermo Electronic) maintained at Ϫ20°C. NADH-tetrazolium reductase (NADH-TR) activity was determined in muscle cross sections as a measure of oxidative potential (32). Cross sections were incubated in a reaction buffer (20 mM MOPS, 1.0 mM nitroblue tetrazolium, and 1.5 mM NADH, pH 7.2) for 30 min at 37°C as previously performed (32).…”

“…NADH-tetrazolium reductase (NADH-TR) activity was determined in muscle cross sections as a measure of oxidative potential (32). Cross sections were incubated in a reaction buffer (20 mM MOPS, 1.0 mM nitroblue tetrazolium, and 1.5 mM NADH, pH 7.2) for 30 min at 37°C as previously performed (32). The resulting staining was visualized with a brightfield Nikon microscope linked to a PixeLink digital camera and quantified with Image-Pro PLUS analysis software .…”