Comparative observations on the growth changes of the histochemical property and collagen architecture of the Musculus pectoralis from Silky, layer-type and meat-type cockerels

Growth‐related changes in the histochemical properties and collagen architecture of the Musculus pectoralis were compared among Silky, layer‐type and meat‐type cockerels. Histochemical and immunohistochemical methods were used and collagen architecture was studied using scanning electron microscopy. The total amount of collagen present was also measured. The diameter of type IIB myofibers was similar or rather larger in the layer‐type birds compared with the meat‐type. The collagen content was generally low for 5–10 weeks across the breeds and then increased in the other breeds except for Silky. In the perimysium, the collagen bundles gradually increased in size and the density of the fibrils also increased during growth. At 30 weeks of age, the layer‐type birds showed compact collagen bundles while the meat‐type had loose bundles. The endomysial collagen network appeared relatively denser in the meat‐type chicks compared to the others at week 1. At 30 weeks of age, compact and felt‐like structure of endomysium was shown by Silky and layer‐type chickens, while the meat‐type showed a relatively loose arrangement of tissue in the endomysial collagen. From these results, it appears that the meat‐type chicken can produce a large M. pectoralis with many, relatively thinner myofibers and a relatively undeveloped form of intramuscular collagen structure.     

Comparative observation on the growth changes of the histochemical properties and collagen architecture of the Musculus puboischiofemoralis pars medialis from Silky, layer-type and meat-type cockerels

Growth‐related changes in the histochemical properties and collagen architecture of the Musculus puboischiofemoralis pars medialis were compared among Silky, layer‐type, and meat‐type cockerels. Histochemical and immunohistochemical methods were employed and collagen architecture was studied using scanning electron microscopy. Total intramuscular collagen was also determined. The myofibers were categorized as type I, type IIA and a transitional form, type I‐tr. The proportion of type I‐tr myofibers diminished and these myofibers were transformed entirely into type I myofibers in meat‐type but incompletely in the others. The largest diameter of type I myofiber was found in layer‐type at 30 weeks of age. At 30 weeks of age, layer‐type birds had attained well‐developed perimysial collagen bundles while meat‐type birds had less developed bundles. The endomysial collagen network had a large mesh size at 1 week and then accumulated many collagen fibrils to form a felt‐like fabric of fibrils by 30 weeks of age. Silky birds developed the thickest endomysial collagen plates of all the breeds. From these results it appears that growth‐related changes in the histological structure of M. puboischiofemoralis pars medialis are not necessarily causally affected by the different growth rates of chicken breeds.     

Comparison of collagen content, distribution and architecture among the pectoralis, iliotibialis lateralis and puboischiofemoralis muscles with different myofiber composition in Silky cocks

The total amount of collagen, the relative distributions of types I and III collagens in perimysium and endomysium, and the collagen fiber architecture were compared among the pectoralis (PT), iliotibialis lateralis (ITL) and puboischiofemoralis (PIF) muscles in Silky cocks. All of the myofibers in the PT muscle were type IIB, the myofibers in the ITL muscle were divided into type IIA, 41.7% and IIB, 58.3%, and the PIF muscle was composed of type I, 24.6%; IIA, 64.6%; and transitional, 10.8%. The total amount of collagen differed significantly among the PT (2.92 mg/g), PIF (4.20 mg/g) and ITL (8.06 mg/g) material, where only the PIF was a whole muscle with epimysium. On the image analysis of the immunohistochemical preparations, the percentage area of perimysial collagen to the total area in each type differed significantly among the PIF, PT and ITL muscles, where it was 26.8, 50.0 and 74.4% for the type I collagen and 27.4, 32.9 and 61.7% for the type III collagen, respectively. In the scanning electron micrography of the perimysium in macerated preparations, thick bundles of collagen fibers were observed in the ITL muscle, thinner but broad platelets in the PT muscle, and a coarse tissue of thinner collagen fibers in the PIF muscle. However, the endomysial fabric of collagen fibrils was similar among the muscles. Small, transverse collagen fibers, which branched off from the thicker perimysia, occupied narrow interendomysial spaces and separated the primary myofiber fasciculi. The results indicate that the ITL muscle, localized in the distorted and overextended part of the leg and subject to strong external forces, had highly developed perimysial collagen fiber bundles, but the ITL endomysial collagen architecture was similar to that of the PT and PIF muscles.     

Age-related changes in the intramuscular distribution of melanocytes in the Silky fowl

1. The characteristics of melanocyte distribution in skeletal muscles in the Silky fowl were investigated in association with growth. 2. Pectoralis (PT) and iliotibialis lateralis (ITL) muscles from 1-, 3-, 5-, 10-, 20- and 30-week-old Silky males were weighed and collagen type I was detected in frozen sections immunohistochemically. 3. Melanocytes were observed in the collagen type I-immunopositive endomysium and perimysium in both muscles. 4. Image analysis indicated that the total area occupied by melanocytes in histological sections sharply decreased from 0.61% to 0.16% in PT muscle and from 1.67% to 0.33% in ITL muscle at 1 to 3 weeks, and then gradually decreased. The melanocyte area was larger in ITL muscle than in PT muscle until 10 weeks of age. 5. We concluded that the proportion of intramuscular melanocytes in the Silky fowl differs between types of muscles in the early stages of development, and it decreases with growth.     

Growth changes of the collagen content and architecture in the pectoralis and iliotibialis lateralis muscles of cockerels

1. Growth changes of the collagen content and architecture in the pectoralis (PT) and iliotibialis lateralis (ITL) muscles were examined using cockerels from 1 to 14 weeks of age. 2. Total collagen content in PT muscle showed little change, but in ITL muscle reached a maximum at 5 weeks and thereafter decreased slightly until 14 weeks. The collagen content was markedly larger in ITL muscle after 5 weeks. Pyridinoline content of collagen increased abruptly from 5 to 14 weeks in both muscles, but no difference between muscle types was detected. 3. The cell size of the endomysial honeycombs increased with the development of myofibres, and the mesh size of the perimysium around the honeycombs enlarged. 4. In both muscles endomysia were an incomplete network of collagen fibrils with many foramina at one week, became a very thin membrane of felt-like fabric in 2 to 5 weeks and thereafter increased in thickness until 11 to 14 weeks. 5. Perimysial width around the secondary fasciculus differed between the muscle types after 5 weeks. In the wider perimysium of ITL muscle, the collagen fibres increased in number and size to make a stack of collagen bands around the fasciculus. In the narrower perimysium of PT muscle, a few platelets of collagen fibres also developed. 6. The perimysial collagen fibre at 1 to 2 weeks had a smooth surface and appeared to be composed of fine collagen fibrils. The fibre at 11 to 14 weeks showed a rugged surface and was composed of coarser collagen bundles that combined with each other into a net-like configuration with very slim meshes. 7. Our results showed that the collagenous components of chicken intramuscular connective tissue changed markedly during the early period of muscle growth in distribution, architecture and quality but with little difference in quantity.     

Developmental states of the collagen content, distribution and architecture in the pectoralis, iliotibialis lateralis and puboischiofemoralis muscles of male Red Cornish x New Hampshire and normal broilers

1. Developmental states of the collagen content, distribution and architecture in the pectoralis (PT), iliotibialis lateralis (ITL) and puboischiofemoralis (PIF) muscles of male Red Cornish x New Hampshire (RN, 80 d, body weight 2.9 kg) and normal (3.1 kg) broilers were evaluated. 2. In PT muscle the total amount of collagen was significantly greater in RN broilers (3.33 mg/g) than in normal ones (1.71 mg/g). This higher collagen content in RN broilers was based mainly on the closer mesh sizes of endomysial honeycomb. The collagen structures in the perimysia also differed between broiler types, when more collagen fibres were observed in RN broilers. 3. ITL muscle contained total collagen of 4.10 to 5.00 mg/g. Types I and III collagens were distributed on the perimysia at higher percentages in RN broilers (31.6%, 37.2%) than normal (15.6%, 30.8%), respectively. The thick bands of tough collagen fibres characteristic of ITL muscle perimysium in cockerels had not yet developed in these broilers. 4. Total collagen was 4.63 to 6.29 mg/g in PIF material with fascia. In PIF muscle the perimysial collagen fibres had not yet attained their full growth but consisted of densely packed fibrils. PIF muscle was characterised by the earlier maturing collagen structure. 5. These results show that a perimysial collagen structure in broilers is still in an undeveloped state. It is supposed that tenderness of broiler meat is attributed mainly to characteristics of the collagen distribution, in which the majority of types I and III collagens is distributed on the closer mesh of endomysial honeycomb.     

Scanning electron microscopic observation of the architecture of collagen fibres in chicken M. iliotibialis lateralis

1. The collagen architecture of M. iliotibialis lateralis in chicken was observed under the scanning electron microscope after muscle maceration in NaOH. 2. Immunohistochemical methods showed Type I and III collagens to be distributed over both perimysium and endomysium. 3. Thick perimysium around secondary myofibre fasciculi was composed of many large longitudinal collagen bundles and a few small circumferential bundles. In contrast, thin perimysium around primary myofibre fasciculi showed mainly circumferential bundles. 4. Endomysium had a honeycomb-like structure and consisted of a fine collagen mesh, its main fibre striation being circumferential. 5. It is suggested that functional demand differs between thick perimysium and thin endomysium.     

Histochemical properties and collagen architecture of M. iliotibialis lateralis and M. puboischiofemoralis in male broilers with different growth rates induced by feeding at different planes of nutrition

1. The histochemical properties and the collagen content and architecture of the iliotibialis lateralis (ITL) and puboischiofemoralis (PIF) muscles were assessed in Red Cornish x New Hampshire cockerels reared on a high nutrient plane for 80 d (H80d), or a low nutrient plane for 80 d (L80d) or 95 d (L95d). 2. Final live weights were 3410 g in H80d, 2810 g in L80d and 3467 g in L95d. Both ITL and PIF muscle weights were lowest in L80d and did not differ between H80d and L95d. 3. ITL muscle was composed of fast-twitch myofibres such as IIA (high reduced nicotinamide adenine dinucleotide dehydrogenase, NADH-DH activity), IIB (low NADH-DH activity) and IIC (intermediate NADH-DH activity). The high percentage of type IIB myofibres in H80d (76.6%) and L95d (76.2%) birds were reflected in low percentages of type IIC myofibres (12.2%) in H80d birds and type IIA myofibres (8.2%) in L95d birds. Percentages of IIA, IIB and IIC myofibres in L80d cockerels were 12.4, 69.8 and 17.6%, respectively. 4. The myofibres in PIF muscle were divided into two basic types, I and IIA, and a transitional form (I-tr) from IIA to I. In the caudal region, all myofibres in H80d and L95d cockerels were type I but in L80d cockerels 15% of myofibres were categorised as type I-tr. In the cranial region, the great majority (52 to 63%) of myofibres were type IIA. Type I myofibres occurred at a higher percentage in H80d (30.5%) than L95d (21.8%) and type I-tr in L95d (15.7%) than H80d (7.3%) and L80d (11.5%). 5. The total amount of collagen was higher in ITL than PIF muscle in every bird group. In both muscles the highest collagen content was in L95d cockerels but the content did not differ between H80d and L80d birds. The thickness of thick and thin perimysia increased with muscle size. The circular collagen fibre in the thick perimysium was larger in ITL (6.1 to 7.0 microm) than PIF (3.7 to 3.8 microm) muscle but did not differ among the bird groups. 6. From these results, it was concluded that feeding on a high nutritional plane promotes growth of the thigh muscles, with accompanying enlargement of the perimysial thickness, no increase in collagen content and various changes of histochemical properties.     

Comparison of the histological and histochemical properties of skeletal muscles between carbon dioxide and electrically stunned chickens

1. Histological and histochemical profiles of Musculus pectoralis (PT, type IIB fibres), M. iliotibialis lateralis (ITL, types IIA + IIB fibres) and M. puboischiofemoralis pars medialis (PIF, type I fibres) were compared in carbon dioxide (37%, 70 s) and electrically (14 V, 5 s) stunned male chickens. 2. Muscle materials were taken at 0, 4 and 24 h from carcases dressed and cooled with ice-water mixture for 30 min. Glycogen and fat contents, and adenosine triphosphatase and reduced nicotinamide adenine dinucleotide dehydrogenase activities of fibres were measured. 3. In PT muscle at 0 h, gas stunned chickens showed many fibres with high glycogen content but those electrically stunned contained few such fibres. Fibres from gas stunned birds had lost almost all their glycogen after 24 h of cold storage. 4. In the ITL muscle of gas stunned chickens at 0 h residual glycogen was observed in type IIB fibres. In contrast, in the electrically stunned birds it was in type IIA, showing the different effects of the stunning methods. During cold storage, glycogen disappeared earlier in type IIB than IIA fibres. 5. In PIF muscle with fibres of low glycogen content, the gas stunned chickens maintained a good fibre structure for 4 h or more, but the electrically stunned had already lost intact fibre structure at 4 h. 6. These results indicated that the carbon dioxide stunning was a better method for chicken welfare and meat quality than electrical stunning.     

Oral ingestion of collagen peptide causes change in width of the perimysium of the chicken iliotibialis lateralis muscle

Skeletal muscle is mainly composed of myofibers and intramuscular connective tissue. Bundles composed of many myofibers, with each myofiber sheathed in connective tissue called the endomysium, are packed in the perimysium, which occupies the vast bulk of the intramuscular connective tissue. The perimysium is a major determination factor for muscle texture. Some studies have reported that collagen peptide (Col-Pep) ingestion improves the connective tissue architecture, such as the tendon and dermis. The present study evaluated the effects of Col-Pep ingestion on the chicken iliotibialis lateralis (ITL) muscle. Chicks were allocated to three groups: the 0.15% or 0.3% Col-Pep groups and a control group. Col-Pep was administered by mixing in with commercial food. On day 49, the ITL muscles were analyzed by morphological observation and the textural property test. The width of the perimysium in the 0.3% Col-Pep group was significantly larger than other two groups. Although scanning electron microscopic observations did not reveal any differences in the architecture of the endomysium, elastic improvement of the ITL muscle was observed as suggested by an increase of the width of perimysium and improved rheological properties. Our results indicate that ingestion of Col-Pep improves the textural property of ITL muscle of chickens by changing structure of the perimysium.     

Collagen content and architecture of the pectoralis muscle in male chicks and broilers reared under various nutritional conditions

Varying chicken growth rates were induced with different nutritional regimes, and the collagen content and architecture of M. pectoralis (PT) were compared among 21‐day‐old chicks and broilers at 80 or 95 days of age. The percentage of muscle weight to live weight was higher in rapid growing chicks (8.4%) than slow growing chicks (6.3%). The 80‐day‐old broilers engaged in compensatory growth after the early slow growth period producing PT muscle at 11% of live weight. The 80‐ and 95‐day‐old chicks with restricted late growth after an early rapid growth period showed PT weight at 8% and 9% of live weight, respectively. Collagen content of the PT muscle markedly decreased from the chicks to the broilers. The collagen concentration was higher in the late‐growth restricted broilers (1.67–1.88 mg/g) than the compensatory growth broilers (1.01–1.10 mg/g). Collagen concentration did not differ between the rapid and slow growing chicks (2.72 and 2.94 mg/g). Scanning electron micrographs showed thick and thin perimysia, and honeycomb endomysia. In the perimysia, a stack layer of collagen platelets and a reticular layer of collagen fiber cords were distinguished and collagen baskets of adipocytes were observed. The perimysial collagen fibers became thicker during growth of the chicks to broilers. However, in the late‐growth restricted broilers, the perimysial collagen fibers seemed to have retarded development compared with the compensatory growth birds. The PT muscle of chickens develops optimally when body growth is enhanced. The PT muscle of the compensatory growth broilers had improved collagen architecture regardless of the marked decrease in collagen content.     

Age and exercise effects on mitochondrial density and capillary fibre ratio in bird leg muscle

1. Muscle fibre composition, capillary-fibre ratio and mitochondrial density of the Iliotibialis lateralis muscle were monitored during growth from the age of 8 weeks to sexual maturity (24 weeks) in sedentary birds and in birds subjected to regular treadmill exercise. 2. The Iliotibialis lateralis muscle consists almost exclusively of type IIA and IIB fibres with a small percentage of "unclassified" fibres. Over the 16-week period of growth there was no change in fibre composition but a marked fibre hypertrophy linked with a fall in the capillary-fibre ratio. Mitochondrial volume density increased with age but this was not significant. 3. Exercise significantly increased the IIA:IIB fibres ratio from 0.77 to 1.1 but had no significant effect on any other measured characteristics. 4. It is concluded that exercise at the intensity and duration employed (10-15 min daily, ca. 70-80% maximum oxygen consumption) has little effect on the growth and development of avian skeletal muscle although there was evidence of an increased oxidative capacity of the muscle.     

Effects of nutritional level on muscle development, histochemical properties of myofibre and collagen architecture in the pectoralis muscle of male broilers

1. The effects of nutritional level on muscle development, histochemical properties of myofibre and collagen architecture in the pectoralis muscle were evaluated using male broilers of Red Cornish x New Hampshire stock, reared on diets of high nutritional value for up to 80 d (H80d) and low nutritional value for up to 80 d (L80d, same age as H80d) or 95 d (L95d, same body weight as H80d). 2. The total live weight and the weight of pectoralis muscle were lower in L80d than in both H80d and L95d. The muscle weight as a percentage of live weight was 8.7% in L80d, 10.7% in H80d and 11.5% in L95d. 3. Pectoralis muscle was composed only of type IIB myofibres and showed no differences in myofibre type composition among the chicken groups. The largest diameter of type IIB myofibres was observed in L95d, followed by H80d and the smallest in L80d. 4. The total amount of intramuscular collagen did not differ among the chicken groups (1.92 to 1.99 mg/g). Types I and III collagens were immunohistochemically detected in both the perimysia and endomysia. The thin perimysia around the primary myofibre fascicles showed larger width in H80d than L80d and L95d, and also the thick perimysia around the secondary fascicles in H80d than L80d. 5. The collagen structure of the perimysium was most developed in H80d, followed by L95d and on the least in L80d. The development of perimysial collagen fibres could be enhanced by a rapid growth rate of the muscle induced by high nutritional level and depressed by a slow growth rate with low nutritional foods. 6. The endomysial collagen architecture was observed as a felt-like tissue of the fibril bundles with many slits. The thinnest endomysial wall was observed in L80d, followed by H80d and the thickest in L95d. 7. From these results, it was indicated that foods of high nutritional value could enhance growth of the pectoralis muscle of broilers, and this is accompanied by hypertrophy of the type IIB myofibres and development of the perimysial collagen architecture.     

Effects of low protein diet and low protein diet supplemented with synthetic essential amino acids on meat quality of broiler chickens

We investigated the effects of a low crude protein (CP) diet and a low CP diet supplemented with synthetic essential amino acids (EAA) on the meat quality of broiler chickens. Twenty‐one‐day‐old chickens were assigned to one of three diets: control, low CP (LCP), or low CP supplemented with EAA (ELCP). The chickens received these diets for 10 days. The shear force value (SFV) and free glutamate content of the Pectoralis major muscle were measured as indicators of the meat toughness and taste. The collagen and crude fat content of the muscle and the cross‐sectional area of myofibers were measured to evaluate the effects of the LCP and ELCP diets on meat toughness. The SFV of the ELCP group was 47% lower than that of the control group (P < 0.01). However, the LCP diet did not affect the SFV. The collagen and crude fat content were not affected by the dietary treatment. The cross‐sectional area was lower in the LCP and ELCP groups (P < 0.05) than the control group. The free glutamate content of muscle was not affected by the dietary treatment. Thus, a low CP diet supplemented with EAA is an effective means of producing tender meat.     

牛旋毛虫病肌组织病理形态学及包囊形成的观察

用旋毛虫对3头牛成功地进行了实验性人工感染,并用光学显微镜和电子显微镜系统观察了牛肌旋毛虫的形态学变化、肌组织的病理变化及旋毛虫包囊的形成。经口感染旋毛虫后第7d,牛肌组织中出现旋毛虫幼虫,呈杆状,位于肌纤维之间。感染后11d,幼虫进入肌纤维之中,呈杆状。感染后19d,幼虫的一端出现弯曲,并开始包囊的形成,感染后27d,幼虫蟠曲,100d以后,形成完整包囊,其形状为梭形或卵圆形。电镜下观察,包囊壁分为内、外两层,外层由胶原微纤维组成,来自增生的内芽肿;内层由不定形基质、不能显示周期性横纹的胶原微纤维和小泡组成,来自受侵肌纤维。     

Histochemical properties of skeletal muscles in Japanese cattle and their meat production ability

The compositional characteristics of the three basic types of myofiber, namely type I (slow‐twitch oxidative), type IIA (fast‐twitch oxidative glycolytic) and type IIB (fast‐twitch glycolytic), are clarified in the skeletal muscles of Japanese Black cattle. The myofiber composition, which is characteristic of the muscles of Japanese Black cattle, markedly changes during their growth, when some type IIA myofibers are transformed into type I or IIB, depending on the different muscles. Independent of these changes with growth, inter‐ and intramuscular variations of myofiber type distribution is evident. The small extensor muscles in deep regions around bone contain a lot of type I myofibers, whereas the large muscles at surface regions have many type II myofibers. Japanese Black cattle have typical white muscles such as the Longissimus thoracis and Semitendinosus, containing half the myofibers as red (type I + IIA). The muscles of Japanese Black cattle show a tendency to contain a higher percentage of type I myofibers than other breeds over an intrabreed variation of the myofiber type composition. In the big muscles such as the Longissimus thoracis and Biceps femoris, a great diversity of myofiber type composition is observed among the different regions. When fattened, heifers produce Longissimus thoracis and Biceps femoris muscles of smaller weight than steers, but in heifers the myofiber size in each type is rather larger. In the Psoas major, Vastus lateralis and Serratus ventralis muscles, heifers contain a higher frequency of red (type I + IIA) myofibers with no differences in myofiber size. Among the several muscles of fattened Japanese Black steers, the percentage distribution of type I myofibers has a positive correlation with the percentage amount of intramuscular fat. From these results, the high potential of Japanese Black cattle to produce marbled beef could be based on the histochemical properties of myofibers in their skeletal muscles.     

Effects of different rearing systems on meat production traits and meat fiber microstructure of Beijing‐you chicken

Beijing‐you is a Chinese local chicken which is raised for both meat and eggs. In the present study, we detected the effects of different rearing systems on growth, slaughtering performances and meat quality of Beijing‐you chickens at 26–40 weeks of age. Six hundred Beijing‐you hens were randomly allocated into two groups at 16 weeks of age and raised in free range or battery cage systems. The body weight, slaughtering performance and meat quality were measured for each group at the ages of 26, 30, 35 and 40 weeks. Some of the traits were dramatically influenced by the two systems, although most of them did not show significant changes. For the meat fiber microstructure, we found that the diameter of thigh and breast muscle fiber in the free range group were significantly increased than in the cage group (P < 0.05) at 26 weeks of age. The ratio of fast muscle fiber in thigh muscle samples of the free range group was significantly reduced compared to that of cage group at both 35 (P < 0.01) and 40 (P < 0.01) weeks of age, indicating that the free range system could promote the transforming of fast muscle fiber to slow muscle fiber.     

Observations on the ultrastructure of equatorial scleral collagen fibrils in sheep eyes

Objective To investigate collagen fibrils of the equatorial sclera in relation to the age‐related changes in eye size in sheep. Animals studied Lambs and outbred ewes. Procedures Sheep eyes (three lamb and three from adult outbred ewes), presumed disease‐free, were processed for transmission electron microscopy (TEM) immediately postmortem. Tissue blocks from the equatorial region were sectioned across fibril bundles orientated along the equator. Micrographs including at least 500 fibrils were projected at 22 000× magnification for measures of fibril diameters (FDs). Results Lamb eyes were smaller than those of adult ewes but equatorial scleral thickness was only marginally less at 0.232 ± 0.013 vs. 0.254 ± 0.012 mm (P value not significant). Scleral tissue was composed of compacted bundles of collagen fibers that tended to be rounder in outer compared to being flatter in inner regions. In typical (normal) appearing regions, FDs were distinctly larger (68–410 nm) in outer sclera compared to inner sclera (63–281 nm). Outer sclera FDs were bimodal averaging 192 ± 58 nm, compared to unimodal distributions at inner locations averaging 156 ± 48 nm (P < 0.001). Some atypical regions, especially at outer‐mid sclera locations, were also noted where the FD distribution was bimodal but also included numerous microfibrils (<50 nm diameter), with similar appearances being found for both lamb and adult ewe eyes. Conclusions The equatorial sclera is a mixture of rounder versus flatter collagen fiber bundles, the former being more likely to be made up of a mixture of both smaller and larger fibrils, as compared to slightly smaller fibrils.     

Ultrastructure of canine articular cartilage: comparison of normal and degenerative (osteoarthritic) hip joints.

Normal canine hip cartilage was compared with cartilage from the degenerative lesions found in young dogs with canine hip dysplasia. The upper 0.5 mm of normal cartilage was characterized. Four distinct layers or zones were found: a layer of fine fibrous material covering the surface, a layer (surface layer) of small (32 nm diameter or less) collagen fibrils tightly packed in bundles and oriented parallel to the surface, a layer (upper layer) or less tightly packed collagen fibrils oriented mostly parallel to the surface with about 33% of the fibrils 64 nm or more, and a layer (intermediate layer) of randomly oriented fibrils with more than 50% of the fibrils 64 nm or larger. Fibril density was high in the surface layer and decreased with depth into the cartilage. In a moderately advanced lesion of degenerative cartilage, there was a layer of amorphous material over the surface. The tightly packed surface layer of small fibrils was absent. The surface itself was uneven and fissued. At depths from the surface comparable to the upper and the intermediate layers in normal cartilage, the proportion of large fibrils was less than in normal cartilage. The overall density of fibrils in degenerative cartilage increased with depth into the tissue. Cells flattened parallel to the surface, with relatively large nuclei, were found in the upper layer of normal cartilage. Cells in the intermediate layers were larger and round. The oblong cells of the upper layer of normal cartilage were not found in any layer of degenerative cartilage. Differences between cells in other layers of normal and degenerative cartilages were minimal. A model for the arrangement of chondrocytes and collagen fibrils for normal and degenerative cartilage was proposed. Ultrastructural changes in degenerative cartilage were prominent in the upper 0.5 mm of cartilage. These changes were changes in the number of collagen fibrils/mum-2 and a change from a characteristic pattern of collagen fibril diameters and orientation found in normal tissue.     

Breed differences in the histochemical properties of the M. iliotibialis lateralis myofibre of domestic cocks.

1. Reduced nicotinamide adenine dinucleotide dehydrogenase (NADH-DH) activity in the M. iliotibialis lateralis was compared histochemically among 7 breeds of cocks. This muscle was composed only of Type-IIA and -IIB fibres. 2. Apparent breed differences were observed in muscle development, the NADH-DH activity in every fibre type, fibre type distribution and fibre diameters. 3. From the results of this study, it was concluded that the muscle characteristics of various breeds were based not only on the fibre type composition, but also the different activities of oxidative enzyme in every type.