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W K Ovalle

Publications and source records attributed to W K Ovalle.

33 records · Page 2Linked to original sources
PubMed1982

Ultrastructural duality of extrafusal fibers in a slow (tonic) skeletal muscle.

Ultrastructural and stereological assessment of the mature avian anterior latissimus dorsi (ALD) muscle showed that it contains two kinds of extrafusal fibers. This fine structural dichotomy of fiber types in the ALD correlated well with their previously reported histochemical duality. Distinct differences occur in sarcomere banding, myofibrillar area, sarcotubular and mitochondrial density, and in morphology of motor-nerve terminals. Both myofiber types in this muscle were interpreted as representing varieties of "slow" or tonic muscle fibers. Both fibers contain myofibrils that, despite differences in cross-sectional area, were large, irregular, and ribbon-shaped, typical of the "Felderstruktur" appearance of true "slow" fibers. Whereas the majority of fibers (type-1) are devoid of well-defined M-bands, the minor fiber population (type-2) exhibit prominent M-bands in the center of each sarcomere. In addition, type-1 tonic fibers contain a significantly lower mitochondrial and sarcotubular volume than the tonic fibers of type-2. While both fiber types exhibit motor-nerve terminals that are small, smooth and punctate in appearance, those on the type-2 fibers often had a number of shallow postjunctional folds. Whether or not these two classes of extrafusal fiber in this muscle represent two separate and distinct types of motor units remains to be determined functionally.

Animals↗
PubMed1980

An ultrastructural study of multifidus muscle in progressive idiopathic scoliosis. Changes resulting from a sarcolemmal defect at the myotendinous junction.

Biopsies of multifidus muscles were procured from patients with idiopathic scoliosis prior to Harrington rod instrumentation. Specimens from both convex and concave sides at the apex of the curve were examined by light and electron microscopy and compared with normal muscle samples. Abnormalities were detected on the concave aspect of the curve and the most dramatic morphological changes were noted at the myotendinous junction. Here a structural defect in the form of discontinuities in the sarcolemmal membranes of some muscle fibres was accompanied by large numbers of intimately-adhering connective tissue cells. Structural disorganization of the associated tendon occurred in conjunction with increased vascularization and with fatty cell and leukocyte infiltration. Further from the myotendon junction, structural lesions appeared more chronic and non-specific subsequent to the incipient sarcolemmal break in the affected muscle fibres. Hypertrophy, atrophy, centralization of nuclei, and disruption of sarcotubular and myofibrillar elements were noted in some muscle cells. While the aetiology of this disorder is unknown, a supposition is made that the primary change is an inherent weakness and subsequent break in the sarcolemma at the myotendon junction. This site is an important clue to the pathogenesis of this disease since it reflects morphological change in rapidly growing tissue occurring at the time of the rapid adolescent growth spurt leading to progression of the scoliotic curve.

Adolescent↗
PubMed1977

Surface morphology of taste buds in catfish barbels.

External taste buds abound on barbels of the adult catfish Corydoras arcuatus. When examined by scanning electron microscopy, they are visualized as a series of punctate, conical elevations projecting from the general surface epithelium. All taste buds were found to be of one type. Both their external and internal surface features could be clearly elucidated on intact barbels and in barbels fractured transversely at various positions along their length. An extensive nerve terminal network penetrates the base of each taste bud. Two populations of elongated cells bearing prominent microvilli project through the central pore at the tip of each bud. One set of microvilli is thicker, longer and more club-shaped than its counterpart. While both are randomly distributed within each central pore, the small, short microvilli appear to outnumber the larger ones. A third population of cells, devoid of any apical microvilli, was also seen in some of the taste buds examined internally. These cells do not project to the external surface and are interpreted as "basal" cells described in previous light and transmission electron microscope studies of taste buds in other vertebrate species. The functional significance of some of these morphological findings is discussed.

Animals↗
PubMed1976

Fine structure of the avian muscle spindle capsule.

The capsule of the muscle spindle from the anterior and posterior latissimus dorsi muscles of the adult domestic chicken has been studied with the electron microscope. As in other species, two distinct portions of the spindle capsule are distinguished: an outer capsule and an inner capsule. The outer capsule is structurally similar to and continuous with the perineural epithelium. Outer capsule cells are noted by the abundance of pinocytotic vesicles and a network of 6-7-nm microfilaments. The disposition of these microfilaments is circumferential with respect to the longitudinal axis of the spindle. It is proposed that they may provide a contractile mechanism for the capsule which may be related to the over-all functioning of the spindle during movements of the muscle. The inner capsule is composed of a contiguous network of cells possessing long cytoplasmic processes which envelop the intrafusal fibers and their nerve endings in sensory equatorial regions of the spindle. These cells may elaborate the fibrillar and amorphous extracellular material found in periaxial spindle space. They also possess modified cilia with a "9+0" microtubular pattern. It is suggested that these cilia may behave as sensory transducers, relating fluid changes in the periaxial space to the intrafusal fiber nerve endings. Capillaries of the non-fenestrated variety commonly traverse the outer and inner portions of the capsule and are usually completely surrounded by tenuous overlapping processes of inner capsule cells. These findings suggest that the spindle capsule plays a role as a metabolically-active diffusion barrier to the entrance of substances from the external milieu.

Animals↗
PubMed1976

Postnatal cytochemical development of muscle fibers in segmental tail muscles of the rat.

Postnatal development of extrafusal and intrafusal muscle fibers was examined histochemically in segmental tail muscles of the rat. At birth all fibers show a strong reaction for myosin ATPase, uniformity in diameter, and homogeneity in staining intensity. During the first postnatal week, the muscle fibers undergo gradual hypertrophy and hyperplasia but they all maintain the same intense homogeneous staining pattern for the enzyme. By day 9, further differentiation of the muscle fibers results in the formation of a second intrafusal fiber type while the extrafusal fibers are still relatively homogeneous. Finally, two kinds of extrafusal fiber and a third type of intrafusal fiber can be distinguished by day 21. This histochemical fiber pattern is essentially maintained in the adult. These findings show that fiber type development in rat tail muscles lags behind the usual time course of myogenesis known to occur in more rostral regions of the animal. It also indicates that histochemical differentiation of intrafusal fibers in these muscles does not parallel that which occurs in extrafusal fibers. It is likely that arrival and initial contact of sensory nerve terminals on developing intrafusal fibers at day 7 directly influences their relatively early histochemical heterogeneity.

Adenosine Triphosphatases↗
PubMed1972

Fine structure of rat intrafusal muscle fibers. The equatorial region.

An ultrastructural study has been undertaken on the equatorial (sensory) region of the rat muscle spindle. Two kinds of intrafusal muscle fibers, a nuclear bag fiber and a nuclear chain fiber, have been identified in this region on the basis of fiber diameter, nuclear disposition, and M-band appearance. The large-diameter nuclear bag fiber contains an aggregation of tightly packed vesicular nuclei, while the small-diameter nuclear chain fiber contains a single row of elongated, well-separated nuclei. Both muscle fibers contain an attenuated peripheral cylinder of myofilaments surrounding a central core of sarcoplasm. Elements of the sarcotubular system, dilatations of the sarcoplasmic reticulum, and the presence of other sarcoplasmic organelles and inclusions are considerably more abundant in the nuclear chain fiber than in the nuclear bag fiber. Leptomeric organelles and membrane-bounded sarcoplasmic granules are present in both intrafusal fiber types and may be situated between the myofibrils or in intimate association with the sarcolemma. The functional significance of some of these structural findings is discussed.

Animals↗
PubMed1971

Fine structure of rat intrafusal muscle fibers. The polar region.

An ultrastructural comparison of the two types of intrafusal muscle fibers in muscle spindles of the rat was undertaken. Discrete myofibrils with abundant interfibrillar sarcoplasm and organelles characterize the nuclear chain muscle fiber, while a continuous myofibril-like bundle with sparse interfibrillar sarcoplasm distinguishes the nuclear bag muscle fiber. Nuclear chain fibers possess well-defined and typical M bands in the center of each sarcomere, while nuclear bag fibers contain ill-defined M bands composed of two parallel thin densities in the center of the pseudo-H zone of each sarcomere. Mitochondria of nuclear chain fibers are larger and more numerous than they are in nuclear bag fibers. Mitochondria of chain fibers, in addition, often contain conspicuous dense granules, and they are frequently intimately related to elements of the sarcoplasmic reticulum (SR). Striking differences are noted in the organization and degree of development of the sarcotubular system. Nuclear bag fibers contain a poorly developed SR and T system with only occasional junctional couplings (dyads and triads). Nuclear chain fibers, in contrast, possess an unusually well-developed SR and T system and a variety of multiple junctional couplings (dyads, triads, quatrads, pentads, septads). Greatly dilated SR cisternae are common features of nuclear chain fibers, often forming intimate associations with T tubules, mitochondria, and the sarcolemma. Such dilatations of the SR were not encountered in nuclear bag fibers. The functional significance of these structural findings is discussed.

Animals↗
PubMedDate not supplied

Abnormal distribution of proteins in the soleus and extensor digitorum longus of dystrophic mice.

Proteins of the whole muscle homogenates of the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) of normal and dystrophic C57BL/6J mice at 4, 8, 12, and 32 weeks of age were resolved on polyacrylamide isoelectric focusing gels. Gels of the normal SOL proteins at all ages contained two bands specific to SOL and not represented in EDL. Gels of normal EDL contained three bands highly amplified in EDL but barely detectable in SOL. The distribution of proteins in dystrophic SOL was abnormal at all age groups studied due, in part, to a decrease in the proportion of SOL-specific proteins relative to other proteins in the muscle. The distribution of proteins in dystrophic EDL appeared abnormal first at 12 weeks due to a decrease in the relative proportion of EDL-amplified proteins. Due to these and other changes, at 32 weeks the dystrophic SOL and EDL were almost indistinguishable on the basis of their proteins' distributions.

Age Factors↗