bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motor units of the primary ankle extensor muscles of the opossum (Didelphis virginiana): Functional properties and fiber types
Authors: Peters S. E. , Mulkey R. , Rasmussen S. A. , Goslow G. E. 
Published: February 2005

AbstractMotor units of the medial gastrocnemius (MG) and the single lateral gastrocnemius/soleus (LG/S) muscles of the opssum (Didelphis virginiana) were found to have uniformly slow contraction times relative to homologous muscles of the cat. Though a broad range of peak tetanic tensions was found among motor units from both muscles, most of the motor units were quite large relative to tension of the whole muscle. Comparison of the relative sizes of motor units showed that those of LG/S are significantly larger and slower than the units of MG. This suggests that the motor units of the two muscles may be differentially recurited during different behaviors.All of the MG and LG/S motor units were highly or moderately resistant to fatigue. Histochemical staining for NADH‐diaphorase activity indicated consistently high levels of the enzyme in all of the fibers of both muscles. Apparently, all of the fast motor units consist of fast oxidative/glycolytic (FOG)‐type muscle fibers. Our data provide functional evidence that the types of myofibrillar ATPase demonstrated by Brooke and Kaiser ('70), are not necessarily correlated to physiological classification of fiber types as slow oxidative (SO), fast oxidative/glycolytic (FOG), and fast glycolytic (FG) (Peter et al., '72).Perhaps compartmentalization of muscle fiber types may be a first step in the separation of muscles into multiple heads during the evolution of specialization to diverse locomotor habits among the mammals.
Ultrastructure of osmoregulatory organs in larvae of the brackish‐water mosquito, Culiseta inornata (Williston)
Authors: Garrett Margaret A. , Bradley Timothy J. 
Published: February 2005

AbstractThe ultrastructure of the Malpighian tubules, ileum, rectum, anal canal, and anal papillae of larvae of the mosquito Culiseta inornata was examined. The Malpighian tubules, rectum, and anal papillae have many of the ultrastructural features characteristic of ion transport tissues, i.e., elaboration of the basal and apical membranes and a close association of these membranes with mitochondria. The Malpighian tubules possess two cell types, primary and stellate. The larval rectum of C. inornata is composed of a single segment containing a homogenous population of cells. In this respect, the larval rectum of C. inornata is distinct from that of saline‐water species of Aedes. The cells in the larval rectum of C. inornata, however, closely resemble those of one cell type, the anterior rectal cells, of the saline‐water mosquito Aedes campestris with regard to cell and nuclear size, the percentage of the cell occupied by apical folds, and mitochondrial density and distribution. No similarities can be found between the rectum of C. inornata and the posterior segment of the saline‐water Aedes, which functions as a salt gland. On this basis, we have postulated that the rectum of C. inornata does not function as a site of hyperosmotic fluid secretion. The ultrastructure of the anal papillae of C. inornata is consistent with a role in ion transport. The significance of these findings to comparative aspects of osmoregulatory strategies in mosquito larvae is discussed.
Morphology of the head skeleton and muscles of the mosquito, Culiseta inornata (Williston) (Diptera: Culicidae)
Authors: Owen William B. 
Published: February 2005

AbstractThe objectives of this research were to investigate the morphology of the head skeleton and muscles of the female mosquito, Culiseta inornata (Williston). The skeletal parts were examined after maceration in KOH. The attachments of muscles were determined by dissection. Observations were made with the aid of a dissecting microscope at 70× and lower. Each skeletal part and muscle is illustrated and described. Conclusions regarding the skeleton are as follows: (1) the clypeal area is composed of an anteclypeus and postclypeus, (2) the suture between the anteclypeus and postclypeus is rigid and cannot function as a hinge, (3) the dorsal wall of the labrum terminates at its union with the anteclypeus, (4) the dorsal and epipharyngeal walls of the labrum are united apically, (5) the gena and postclypeus are not separated by a suture, and (6) the labellum is composed of three segments and the furca, of some authors, is absent. Twenty‐five muscles were identified, and the origin, insertion, and action of each is described. The tormo‐epipharyngalis muscle is attached anterior to the cibarium and fulcral plates. Its origin is on the clypeal apodeme and the insertion is on the epipharynx. This result confirms earlier reports and disagrees with some recent authors. The maxillary teeth are not designed to draw the fascicle into the tissues, but the cervical and leg muscles accomplish the probing process during feeding on a host. An undescribed muscle of the mandible is reported.
Facial morphology and vibrissal movement in the golden hamster
Authors: Wineski Lawrence E. 
Published: February 2005

AbstractThe major cranial vibrissae in the golden hamster can be moved in complex ways that suggest they are served by a finely controlled motor system. Movements are hypothesized to be the products of (1) differential blood flow and pressure regulation in the sinus surrounding each vibrissal follicle, (2) contractions of the striated facial muscles, and (3) elastic rebound in the connective tissues. The vasculature contributes hydrostatic forces that (a) erect the vibrissae slightly and distort their connective tissue bedding, (b) rigidify the vibrissal capsules, thus forming firm bases of attachment for certain facial muscles, and (c) theoretically provide a pressure plate around the follicle, important in lowering the firing thresholds of receptor endings. The facial muscles supply the major forces in erection and protraction of the vibrissae by acting on both the capsules and the connective tissue bedding. The connective tissues are organized into capsular and extracapsular systems that serve to stabilize the vibrissae and return them to initial rest positions.The slight movements of the genal vibrissa are the effects of vascular and connective tissue dynamics, the musculature being uninvolved. Wide angle movements of the supraorbital vibrissae are products of the vasculature and connective tissues, plus contractions of the Mm. orbicularis oculi and frontalis. Mystacial vibrissal movement is quite complex. The vasculature supplies a small degree of capsular erection and mystacial pad distortion, but primarily rigidifies the capsules. The bulk of erection and protraction is produced by the M. nasolabialis profundus (NLP) and the vibrissal capsular muscles (VCM). The NLP distorts the mystacial pad; the VCM tilt the capsules relative to the pad. Retraction is mainly accomplished by elastic rebound in the pad, this being aided in its extreme degrees by the Mm. nasolabialis and maxillolabialis. The Mm. nasolabialis superficialis and buccinator pars orbicularis oris help to spread the vibrissae into a dorsoventral fan and stabilize the mystacial pad during whisking.
The ontogeny of shell secrtion in Terebratalia transversa (brachiopoda, articulata) II. Formation of the protegulum and juvenile shell
Authors: Stricker Stephen A. , Reed Christopher G. 
Published: February 2005

AbstractThe fine structure of the shell and underlying mantle in young juveniles of the articulate brachiopod Terebratalia transversa has been examined by electron microscopy. The first shell produced by the mantle consists of a nonhinged protegulum that lacks concentric growth lines. The protegulum is secreted within a day after larval metamorphosis and typically measures 140–150 μm long. A thin organic periostracum constitutes the outer layer of the protegulum, and finely granular shell material occurs beneath the periostracum. Protegula resist digestion in sodium hypochlorite and are refractory to sectioning, suggesting that the subperiostracal portion of the primordial shell is mineralized. The juvenile shell at 4 days postmetamorphosis possesses incomplete sockets and rudimentary teeth that consist of nonfibrous material. The secondary layer occurring in the inner part of the juvenile shell contains imbricated fibers, whereas the outer portion of the shell comprises a bipartite periostracum and an underlying primary layer of nonfibrous shell. Deposition of the periostracum takes place within a slot that is situated between the socalled lobate and vesicular cells of the outer mantle lobe. Vesicular cells deposit the basal layer of the periostracum, while lobate cells contribute materials to the overlying periostracal superstructure. Cells with numerous tonofibrils and hemidesmosomes differentiate in the outer mantle epithelium at sites of muscle attachments, and unbranched punctae that surround mantle caeca develop throughout the subperiostracal portion of the shell. Three weeks after metamorphosis, the juvenile shell averages about 320 μm in length and is similar in ultrastructure to the shells secreted by adult articulates.
Energy of the oscillating legs of a fast‐moving cheetah, pronghorn, jackrabbit, and elephant
Authors: Hildebrand Milton , Hurley James P. 
Published: February 2005

AbstractLifelike models of the oscillating legs treated as three‐segment systems show the course of kinetic and potential energy over the locomotor cycle for a cheetah, pronghorn, jackrabbit, and elephant running at speeds approaching their maxima. The models can be adjusted to eliminate differences among the animals in time intervals, mass or length of limb, and joint angles. This facilitates analysis of the influence on total energy of each of these variables and of the distribution of mass among leg segments. Fast‐cycling legs of the carnivore type have significantly more energy than those of the hoofed type. This may contribute to the lesser endurance that is usual for carnivores that hunt using a high‐speed dash.
Intricate sutures as fractal curves
Authors: Long Charles A. 
Published: February 2005

AbstractThe study of fractal dimensionality for complex sutures in deer skulls and ammonites reveals their extremely long and elaborate lengths in relation to the defined areas they bound. These sutures often show various scales of self‐similarity (where the parent pattern is elaborated in miniature, again and again), and empirical fractal dimensions calculated lie between one and two. In the scaling elaborations of Cervid sutures, some elaborations seem isolated from the continuous suture. Small “islands” are seen in similar theoretical fractal curves as well. The evolutionary and developmental specialization of intricate sutures improves the bonds; such fitness is essential owing to extraordinary stresses. Autocorrelation (where nearby sides or elaborations tend to resemble a basic pattern and, therefore, resemble one another) of the elaborations of the sutures serves to lengthen the boundaries and theoretically enhances the development of self‐similar patterns. When autocorrelation and self‐similarity in the sutures are favored by an evolutionary process plastic enough to elaborate intricate form, ensuring fitness, and natural selection does not directly limit the lengths while concomitantly defining the bounded areas, then the intricacy is manifest as fractal phenomena, and practically described as such.
Surface ultrastructure of the gill arch of the killifish, Fundulus heteroclitus, from seawater and freshwater, with special reference to the morphology of apical crypts of chloride cells
Authors: Hossler Fred E. , Musil George , Karnaky Karl J. , Epstein Franklin H. 
Published: February 2005

AbstractThe surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf‐like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 × 4 μm and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 μm2, and occurred at a frequency of about 1 per 70 μ2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 μ2), occurred less frequently (1 per 123 μ2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.
The silk and silk production system of the funnel‐web mygalomorph spider Euagrus (Araneae, Dipluridae)
Authors: Palmer Jacqueline M. 
Published: February 2005

AbstractThe silk production systems of several specimens representing at least three species of the mygalomorph genus Euagrus were examined by dissection and by a variety of absorption and fluorescent histochemical techniques. The intrageneric variation is primarily restricted to gland number, with larger numbers of glands in the larger‐bodied species. The silk glands are arranged in four groups each serving one of four spinnerets. Spigot morphology is uniform, consisting of a long, slender shaft of slightly variable length emerging from an enlarged sac‐shaped base. Only one gland type is identified histochemically, although a considerable range in size and shape is observed. Each gland has three secretory zones, a distal one that produces a largely hydrophobic protein core and medial and proximal zones that produce distinct charged protein coatings. Amino acid analysis of the silk indicates a composition very similar to the frame threads and draglines of araneomorph spiders. The high percentage of short side‐chain amino acids implies a polymer structure able to support the suspended entrapment web found in Euagrus and its relatives (but which is rare in most other nonaraneomorph families). Dry silk examined under high magnification appears smooth and homogenous. The fact that in the web larger threads appear to fibrillate suggests that Euagrus silk is polyfilamentous.
New data on the structure and the growth of the osteoderms in the reptile Anguis fragilis L. (Anguidae, Squamata)
Authors: Zylberberg L. , Castanet J. 
Published: February 2005

AbstractLight and electron microscopy shows the osteoderms of Anguis fragilis to be small, flat disks located in the dermis along the adult trunk: microradiography established the extent of the mineralization.Each osteoderm coincides exactly with an epidermal fold forming the keratinized scales characteristic of the skin of reptiles.Sections perpendicular to the surface show two mineralized layers differing in histological and histochemical characteristics and in fine structure, although both contain collagen fibrils. The structure of each layer can be related to that of the surrounding dermis.The outer superficial layer located in the loose dermis contains few collagen bundles that form a discontinuous sheet at the upper surface of the osteoderms. This superficial layer appears to be constituted of units separated by furrows and is composed of woven fibered bone.The basal plate comprises stratified lamellae formed of parallel‐oriented collagen fibrils; the fibrils of successive lamellae lie at right angles. The densely packed collagen fibrils of the basal plate are distributed similarly to those of the dense dermis within which it lies. This layer exhibits structural and histochemical characteristics of a lamellar bone.The presence of two different layers in the osteoderms of Anguis fragilis may reflect their mode of formation, which consists of the deposit of mineral crystals in the preexisting dermal tissue. This mineralization process, considered as a “metaplastic ossification,” may reflect the potentiality retained by the dermis of reptiles to form mineralized structures.
Comparative limb myology of four arvicolid rodent genera (mammalia, rodentia)
Authors: Stein Barbara R. 
Published: February 2005

AbstractA comparative study of four genera of arvicolid rodents (Clethrionomys, Eothenomys, Alticola, and Synaptomys) presents the first complete description of limb myology for any member of this recently evolved, highly successful family. The study also identifies four forelimb and four hind‐limb muscles that exhibit characters of value to systematic analyses within the group. In no instance was postcranial myology sufficient to distinguish among species of Clethrionomys or to distinguish Clethrionomys from Eothenomys. Moreover, in some instances Synaptomys, a genus traditionally presumed primitive within the family, possessed the apomorphic condition for a myological character when compared to the four genera of cricetine rodents that served for outgroup comparisons.
Cytoskeletal organization and tissue patterns of epithelia in the sponge Ephydatia mülleri
Authors: De Ceccatty Max Pavans 
Published: February 2005

AbstractComparative morphological studies on cytoskeletal patterns of sponge basal epithelium at the tissue level have been performed by diverse methods, including immunofluorescence microscopy, and scanning and transmission electron microscopy of stained whole mounts, thin sections or replicas. These methods give results consistent with each other and show the importance of actin assemblies, which function in addition to the microtubular system and in the absence of intermediate filaments. Actin microfilaments indeed are involved in the formation of cables and networks closely associated with the plasma membrane. Both the cables and the networks result from arrangements of microfilaments into bundles of variable size, and the two types of assembly are probably interconvertible. Microfilaments appear to be implicated in the establishment of spot desmosomes and as devices for cell‐to‐substratum attachment. Due to the desmosomal articulations from cell to cell, the actin cytoskeleton is framed throughout the complete epithelium. It supports the unitary nature of the entire tissue, which is constructed and functions as a whole. It therefore establishes the “histoskeleton” of basic epithelial tissues. The histoskeleton is involved in all epithelial activities but is not uniformly organized into identical cell patterns at the tissue level because activities are sequential and not synchronized in all cells. Similar cytoskeletal patterns exist only in groups of cells, and this suggests that, at a given time, the multiple functions of the epithelium may be mediated by the occurrence of several multicellular functional units within a single epithelial tissue.
Anterior alimentary canal of the pear Psylla,Psylla pyricolafoerster (Homoptera, Psyllidae)
Authors: Ullman Diane E. , McLean Donald L. 
Published: February 2005

AbstractScanning and light microscopy investigations of the anterior alimentary canal of the pear psylla,Psylla pyricolaFoerster (Homoptera: Psyllidae), revealed the morphology of the labium and stylets, as well as the presence of sensory structures and a valve in the precibarium. The labium consists of three telescoping segments with an internal labial groove, which surrounds and supports the stylet bundle. Also a part of the labial groove is the internal labial clamp. The stylet bundle is comprised of paired styliform mandibles and maxillae, which interlock to form the food and salivary canals. The stylet bundle proximal to the labium forms a large loop within a membranous crumena. When fully retracted the coiled stylets are under tension. Stylet extension generates increasing tension so that when retracted the stylets readily recoil within the crumena. Penetration of leaf tissues by the stylet bundle is dependent on the interaction between stylet muscles, opening and closing of the labial clamp, the barbed stylet tips, and the ventral position of the labium.Proximal to the crumena the paired stylets separate and diverge at the entrance of the precibarium, which is formed by the interlocking of the epi‐and hypopharynges. There are 18 sensory structures in the precibarium, as well as a precibarial valve. These structures appear to be homologous to similar structures observed previously in aphids and leafhoppers. The morphology and the location of the precibarial sensilla suggest that, like the precibarial sensory organs of aphids and leafhoppers, they are gustatory and probably mediate acceptance or rejection of plant fluids, thus playing a major role in locating tissues for feeding.
Cell wall structure and composition in the comb built by hornets and wasps (Vespinae, hymenoptera)
Authors: Ganor Eliezer , Barenholz–Paniry Vered , Ishay Jacob S. 
Published: February 2005

AbstractMorphological, mineralogical, and chemical investigations were undertaken to determine the structure and composition of the cell walls of the comb in the nest of Vespa orientalis, Paravespula germanica, and Vespacrabro. Nests of V. orientalis were from three sites having different soil types, namely, Khamra soil, Gramosol soil, and organically rich soil from the city dump in Tel Aviv. Nests of P. germanica were from areas rich in organic matter, and those of V. crabro, shipped from Austria, were similarly comprised of organic matter. Structure and composition of cell walls in the three species differed; furthermore, grain size in the combs differed from that of particles in the surrounding soil.
Soft‐tissue bone interface: How do attachments of muscles, tendons, and ligaments change during growth? A light microscopic study
Authors: Hurov Jack R. 
Published: February 2005

AbstractThis study addressed the problem of how soft structures maintain approximately the same relative positional relationships during long bone growth. Attachments of the popliteus muscle, semitendinosus tendon, medial collateral knee ligament, and extensor retinaculum were examined histologically in rabbits, aged 2–60 days, to determine the manner in which soft structures attached to long bones during growth. Soft structures inserted principally into fibrous periosteum or perichondrium in the age range studied. However, an extensive collagen fiber framework within the cellular periosteum and perichondrium, present by at least 2 days of age, linked the fibrous periosteum or perichondrium to subjacent bone or cartilage. Maturation of soft tissue‐bone interfaces was viewed from two related perspectives. The first stressed temporal patterning of cartilage and bone differentiation. The second emphasized incorporation of attachments of soft structures into bone and cartilage matrices during growth and remodeling. Differentiation and remodeling of bone and cartilage varied not only with age, but also between regions of attachment of single muscles and ligaments. Insertion regions were characterized by the presence of coarse‐fibered periosteal bone and chondroid bone, both morphologically intermediate between fibrocartilage and lamellar bone. These results provide evidence that periosteal attachments, characterizing the soft‐tissue bone interface, are a necessary structural prerequisite for compensatory movement and invariance of the relative positions of muscles, tendons, and ligaments during long bone growth.