Localization of myoglobin in striated muscle of the domestic pig; benzidine and NADH2-TR reactions

Influence of rearing conditions and crossbreeding on muscle color in Iberian pigs Influencia de las condiciones de crianza y del cruce en el color de los músculos de cerdos Ibéricos

The effects of pig crossbreeding (Iberian versus Iberian x Duroc 50%) and rearing conditions (out doors versus indoors) on muscle fiber composition, myoglobin content and objective muscle color in biceps femoris and tibialis crancalis muscles have been studied. Muscle fibers were identified as types I, IIA, IIB, oxidative IIB and IIC and the proportion of each fiber type was determined by a computer ized image analysis. Color co-ordinates L*, a*, and b* were measured and both chroma ( C*) and hue angle ( h°) were calculated. Myoglobin content and chroma value were significantly higher in tibialis cranealis muscle than in biceps femoris muscle ( p ≤ 0.001), whereas the former muscle showed the lowest lightness and hue angle values ( p ≤ 0.001). Moreover, tibialis cranealis muscle exhibited a higher total proportion of oxidative fibers, types I, IIA and IIBx ( p ≤ 0.05), and a lower fat content than did biceps femoris muscle ( p ≤ 0.001). The muscles of pigs reared outdoors tended to show a higher per centage of oxidative fibers (type I) than did muscles from indoor reared pigs, although not to a sig nificant extent. Rearing conditions significantly affected color, muscles from outdoor reared pigs ex hibiting higher lightness ( L*), chroma ( C*) and hue angle ( h°) than muscles from indoor reared pigs. However, neither the crossbreeding nor the rearing conditions showed a significant influence on myoglobin concentration of muscles.

Histo- and biochemical characteristics of the Longissimus dorsi muscle in pigs and their relationships to performance and meat quality

Histo- and biochemical characteristics of the longissimus dorsi muscle at 65-70 kg body weight and their relationships to performance and meat quality at 100 kg were examined in Danish Landrace and Danish Large White female and castrated male pigs. Breed differences were observed for feed conversion rate, and a number of histochemical and biochemical traits. The organoleptic traits, flavour (13%), tenderness (15%) and overall acceptability (13%) were rated higher in Large White pigs. Significant correlations between histological and biochemical traits of the live muscle on the one side and performance, meat quality and organoleptic traits on the other side, could be demonstrated. However, these correlations were generally low (r < 0.35), and can thus only explain a small part of the variation in the measured quality traits. Consequently live muscle traits measured at 65-70 kg are poor predictors of meat quality characteristics after slaughter at 100 kg.

Facilitated transport of oxygen in the presence of membranes in the diffusion path

Most of the experimental observations on facilitated transport have been done with millipore filters, and all the theoretical studies have assumed homogeneous spatial properties. In striated muscle there exist membranes that may impede the diffusion of the carrier myoglobin. In this paper a theoretical study is undertaken to analyze the transport in the presence of membranes in the diffusion path. For the numerical computations physiologically relevant values of the parameters were chosen. The numerical results indicate that the presence of membranes tends to decrease the facilitation. For the nonlinear chemical kinetics of the reaction of oxygen with the carrier, this decrement also depends on the location of the membranes. At the higher oxygen concentration side of each membrane the flow of combined oxygen is transferred to the flow of dissolved oxygen. The reverse process occurs at the lower concentration side. Jump discontinuities of the concentration of the oxygen-carrier compound at each membrane are associated with these transfers. The decrement of facilitation is due to the cumulative effect of these jump discontinuities.

Element analysis of skeletal muscle in Duchenne muscular dystrophy using x-ray fluorescence spectrometry

Concentrations of calcium, iron, copper, and zinc were simultaneously measured by x-ray fluorescence spectrometry in muscle biopsies from 11 normal subjects, 13 patients with Duchenne muscular dystrophy (DMD), and 3 DMD carriers. Calcium and copper levels were significantly elevated in patients with DMD compared to controls, and one presumptive carrier also showed an elevated calcium concentration. Comparisons with morphological data for the same samples showed a significant positive correlation between calcium concentration and the percentage area of type 2 fibers in controls, but no other correlations were found to be significant. These results illustrate the value of x-ray fluorescence spectrometry and provide further evidence for the involvement of calcium in dystrophic processes.

Histochemical and ultrastructural characteristics of a new muscle fibre type in avian striated muscle

The serratus metapatagialis (SMP) muscle of the pigeon has been studied histochemically and ultrastructurally. At the gross anatomical level the SMP is clearly divisible into a peripheral whitish band and a red portion comprised predominantly of 'pale' and 'red' fibres respectively. The pale fibres possess low succinate dehydrogenase, low mitochondrial content, absence of subsarcolemmal mitochondrial aggregates, low fat, moderate glycogen, high phosphorylase, low-to-moderate regular myofibrillar adenosine triphosphatase (M-ATPase), activation of M-ATPase following acid preincubation and jagged Z bands. On the basis of these characteristics, these physiologically slow muscle fibres have been termed 'Type I white or slow-twitch glycolytic'. The SMP red fibres, however, possess high aerobic as well as glycolytic capacity, high M-ATPase activity which is labile after acid preincubation and thick but straight Z bands; therefore, they are the 'Type II red or fast-twitch oxidative-glycolytic'.

Permeability of muscle capillaries to exogenous myoglobin

Whale skeletal muscle myoglobin (mol wt 17,800; molecular dimensions 25 x 34 x 42 A) was used as a probe molecule for the pore systems of muscle capillaries. Diaphragms of Wistar-Furth rats were fixed in situ at intervals up to 4 h after the intravenous injection of the tracer, and myoglobin was localized in the tissue by a peroxidase reaction. Gel filtration of plasma samples proved that myoglobin molecules remained in circulation in native monomeric form. At 30-35 s postinjection, the tracer marked approximately 75% of the plasmalemmal vesicles on the blood front of the endothelium, 15% of those located inside and none of those on the tissue front. At 45 s, the labeling of vesicles in the inner group reached 60% but remained nil for those on the tissue front. Marked vesicles appeared on the latter past 45 s and their frequency increased to approximately 80% by 60-75 s, concomitantly with the appearance of myoglobin in the pericapillary spaces. Significant regional heterogeneity in initial labeling was found in the different segments of the endothelium (i.e., perinuclear cytoplasm, organelle region, cell periphery, and parajunctional zone). Up to 60 s, the intercellular junctions and spaces of the endothelium were free of myoglobin reaction product; thereafter, the latter was detected in the distal part of the intercellular spaces in concentration generally equal to or lower than that prevailing in the adjacent pericapillary space. The findings indicate that myoglobin molecules cross the endothelium of muscle capillaries primarily via plasmalemmal vesicles. Since a molecule of this size is supposed to exit through both pore systems, our results confirm the earlier conclusion that the plasmalemmal vesicles represent the large pore system; in addition, they suggest that the same structures are, at least in part, the structural equivalent of the small pore system of this type of capillaries.