bluuebunny/crossref_metadata_2025_split huggingface dataset:
Keratin formation and barrier mechanisms in the epidermis of Natrix natrix (Reptilia: Serpentes): An ultrastructural study
Authors: Landmann Lukas 
Published: February 2005

AbstractA β‐keratin pattern, consisting of 30 Å filaments embedded in an amorphous matrix, is formed by fusion of membrane‐bound packets with the 70 Å filaments of immature cells. This pattern occurs in the Oberhäutchen and the β‐layer. When completely mature, these two components show no cell boundaries. It is suggested that this feature is associated with the process that leads to the separation of outer and inner epidermal generation. Filaments of 100‐150 Å embedded in an amorphous matrix form the α‐keratin pattern, which occurs in the α‐layer only. The lacunar tissue is regarded as consisting of cells resembling immature α‐cells, whereas mesos and clear layer show a keratin‐like material consisting of 100‐150 Å filaments without matrix. This is regarded as a modification of α‐keratin. The cells of all components synthesizing α‐keratin (α, mesos and clear layer) have the following features in common: (1) the plasma membrane is modified in that its inner leaflet is obscured by the deposition of a marginal layer, and (2) the cells have 0.06‐0.1 μm mucous granules containing mucopolysaccharides, which release their content into the intercellular space.Protective and barrier functions of the epidermis are provided by the following features: (1) Oberhäutchen and β‐layer merge during final maturation to a homogenous stratum of β‐keratin without intercellular spaces. Their function seems to be mechanical protection. (2) The marginal layer of α‐keratin containing cells, which decreases in thickness from without inwards, is highly resistant to physical and chemical influences. (3) Mesos granules contain phos‐pholipid‐lamellae, which are partly discharged into the intercellular space and partly remain within the mesos cells. These lipid lamellae are believed to contribute to the establishment of the permeability barrier. (4) The content of mucous granules may play a role in immunological processes. (5) Tight junctions seal off the intercellular space between the uppermost living cells of the epidermis and contribute to the permeability barrier.
Colic modifications in iguanine lizards
Authors: Iverson John B. 
Published: February 2005

AbstractAll lizard species of the subfamily Iguaninae except Amblyrynchus cristatus possess from one to eleven transverse valves in the proximal colon. Valves are of two kinds: circular (sometimes with a sphincter valve) or semilunar. Circular valves (if present) always occur proximally to semilunar valves. Intraspecific variation in the number and type of valves is small, but increase with modal number of valves. No significant ontogenetic change in number of valves could be demonstrated. Colic valves in iguanine lizards apparently evolved as simple infoldings of the medical colic wall.Comparisons are made with colic modifications occurring in other lizard families. Herbivorous species of the Scincidae, Agamidae, and Iguanidae are the only lizards known to exhibit colic partitioning, suggesting that the evolution of these structures is intimately related to the evolution of herbivory in these lizards. The potential taxonomic and phylogenetic importance of lizard colon anatomy is discussed.
Regeneration of colonic mucosa in the rat
Authors: Brackett Kim A. , Townsend Samuel F. 
Published: February 2005

AbstractAs part of a study of ulcer formation and healing, regeneration of colonic mucosa in rats was studied following placement of a surgical lesion. Alterations in mucosubstances and connective tissue were examined and their possible significance discussed.The sequence of events in healing was: (1) The mucosa adjacent to the lesion tipped into the lesioned area. The crypts in this mucosa became lined with cells which contained no mucus and had no striated borders. Later in the experimental period, these undifferentiated cells gave rise to cells containing carboxymucins. Cells containing sulfomucin, neutral mucin, or having striated borders arose from the carboxymucin cells. (2) An epithelial ledge of undifferentiated cells migrated onto a sulfated glycosaminoglycan, fibrous interface between necrotic and living tissue in the lesion. (3) Crypt formation began with the appearance of intraepithelial anlagen. (4) Crypts lengthened by a process of epithelial‐connective tissue proliferation from the base of the crypt upwards. Following completion of connective tissue regeneration, crypts formed by invading the reestablished lamina propria. (5) The first mucous cells in the ledge contained carboxymucins. As crypt formation occurred, these cells gave rise to typical columnar absorptive cells, to cells containing sulfomucins, and to cells containing neutral mucins. (6) Lengthening of crypts ceased following the appearance of a sulfated acid glycosaminoglycan—collagenous layer deep in the submucosa.
Quantitative assay of electromyograms during mastication in domestic cats (Felis catus)
Authors: Gorniak Gerard C. , Gans Carl 
Published: February 2005

AbstractMastication has been studied by cinematography with synchronized electromyography (computer quantified and analyzed), while unanesthetized, freely feeding cats (Felis catus) were reducing equivalent‐sized chunks of raw and cooked beef and cooked chicken. Cats reduce food on one side at a time, and their chewing cycles show both horizontal and anteroposterior deflections. Food objects are shifted from side to side by lateral jerks of the head and movements of the tongue.During the opening phase, the lower jaw is rotated relatively straight downward, and the digastric muscles are active in bilateral symmetry. Near the end of opening, the head jerks upward, both zygomaticomandibulares start to fire, and opening acceleration of the mandible decreases. Closing starts with horizontal displacement of the mandibular canines toward the working side, accompanied by asymmetrical activities from the working side deep temporalis and the balancing side medial pterygoid, as well as a downward jerk of the head. As closing proceeds, the mandibular canines remain near the working side and the working side zygomaticomandibularis and deep masseter are very active. Near the end of closing, the mandibular canine on the working side moves toward the midline, and adductors, digastrics, and lateral pterygoids of both sides are active. The adductors of the working side are generally more active than those of the balancing side.During a reduction sequence, the number and shape of the masticatory cycles, as well as movements of the head, during a reduction sequence are affected significantly by food type. As reduction proceeds, the duration of bite and the muscular activity (as characterized by number and amplitude of spikes) change significantly among muscles of the working and balancing sides. The adductors of the working side are generally most active when cats chew raw beef, less for cooked beef, and least for cooked chicken. In general, the adductor activity reflects food consistency, whereas that of the digastrics and lateral pterygoids reflects more the vertical and lateral displacements of the mandible. Statistical analysis documents that the methods of electrode insertion and test give repeatable results for particular sites in different animals. Thus, it should be possible to compare these results with those produced while other mammalas are masticating.
The ultrastructure of the otolithic membrane and otolith in the juvenile mummichog, Fundulus heteroclitus
Authors: Dunkelberger Dana G. , Dean John Mark , Watabe Norimitsu 
Published: February 2005

AbstractThe sagitta otolithic membrane of Fundulus heteroclitus consists of two different zones. A structured zone (gelatinous layer), which usually exhibits a reticulated or honeycomb‐like architecture, is composed of tightly arranged fibrous material and covers only the sensory region of the macula. The gelatinous layer extends from the otolith surface to the tips of the sensory hairs, and probably functions primarily as a mechanoreceptor. The arrangement of this zone is closely associated with specific overlying structural features of the otolith surface and may also influence the pattern of mineral deposition to some degree. A nonstructured zone (subcupular meshwork) consists of fibers in very loose networks and covers both sensory and nonsensory regions of the macula. Over the sensory region, some of this fibrous material extends from the epithelial surface, through pores in the gelatinous layer, to the surface of the overlying otolith. In the nonsensory region, fibers of the subcupular meshwork are relatively more numerous and extend around the peripheral margin of the otolith. Evidence is presented which suggests that the fibrous material of the subcupular meshwork is incorporated into the otolith as an organic matrix constituent. New aspects on the ultrastructure of the otolith are presented and discussed.
Fine structure and distribution of epidermal projections associated with taste buds on the oral papillae in some loricariid catfishes (Siluroidei: Loricariidae)
Authors: Dana Ono R. 
Published: February 2005

AbstractTwo morphologically distinct structures occur on the surfaces of the oral papillae in several loricariid catfish species; namely, (1) typical vertebrate taste buds composed of receptor and sustentacular cells and (2) brushlike projections, termed epidermal brushes, that represent specialized epidermal cells containing keratin. Both of these structures were studied with the combined use of light microscopy and scanning and transmission electron microscopy. The general body surface, fins, and rostral cutaneous processes of some loricariid catfishes are covered with taste or terminal buds but lack the epidermal brushes. It is suggested that the epidermal brushes found on the oral papillae serve as protective devices for the taste buds and as abrasive surfaces for substrate scraping during feeding. The taste buds on the oral papillae may detect any gustatory stimuli from the resulting substrate disturbance. Comparative studies reveal many differences in the number and spatial arrangement of these two structures on the oral papillae among the several species of the Loricariidae examined. These differences may represent functional adaptations to the various modes of life in the Loricariidae.
The functions of the lumbar spine during stepping in the cat
Authors: English Arthur Wm. 
Published: February 2005

AbstractTo examine the functional roles played by the lumbar spine during overground stepping, seven adult cats were run in electromyographic (EMG) experiments. Recordings were made bilaterally from mm. iliocostalis, longissimus dorsi and multifidus at a single vertebral level (L3) and from m. rectus abdominis. Stepping movements were monitored synchronously either by videotape or by high speed cinematography. During alternate use of the hindlimbs (walking and trotting), both epaxial and abdominal muscles were active bilaterally and biphasically. During in‐phase use of the hindlimbs (galloping and half‐bounding), single bursts of activity were observed. Phasic bursts of activity in rectus abdominus were reciprocal to those of epaxial muscles. Second bursts of activity in either group were noted infrequently. Recordings from the same back muscle at several vertebral levels indicated little difference from these patterns. Movements of the lumbar spine during galloping and half‐bounding steps, both angular and linear, are easily correlated with muscle activity patterns. Movements of the lumbar spine during walking and trotting show no particular pattern. Only small angular and linear movements are found. It is concluded that the lumbar spine contributes substantially to step length and limb speed during galloping and half‐bounding steps and the epaxial and abdominal musculature may also act as elastic bodies. During walking and trotting steps, the epaxial muscles are proposed to act to stabilize the pelvic girdle to provide a firm base for limb muscles which arise on the pelvis and are synchronously active.
Intrinsic organization of snake lateral cortex
Authors: Ulinski Philip S. , Rainey W. Todd 
Published: February 2005

AbstractLateral cortex is the most laterally placed of the four cortical areas in snakes. Earlier studies suggest that it is composed of several subdivisions but provide no information on their organization. This paper first investigates the structure of lateral cortex in boa constrictors (Constrictor constrictor), garter snakes (Thamnophis sirtalis), and banded water snakes (Natrix sipedon) using Nissl and Golgi preparations; and secondly examines the relation of main olfactory bulb projections to the subdivisions of lateral cortex using Fink‐Heimer and electron microscopic preparations.Lateral cortex is divided on cytoarchitectonic grounds into two major parts called rostral and caudal lateral cortex. Each part is further divided into dorsal and ventral subdivisions so that lateral cortex has a total of four subdivisions: dorsal rostral lateral cortex (drL), ventral rostral lateral cortex (vrL), dorsal caudal lateral cortex (dcL) and ventral caudal lateral cortex (vcL). Systematic analyses of Golgi preparations indicate that the rostral and caudal parts each contain distinct populations of neurons. Rostral lateral cortex contains bowl cells whose dendrites arborize widely in the outer cortical layer (layer 1). The axons of some bowl cells can be traced medially into dorsal cortex, dorsomedial cortex and medial cortex. Caudal lateral cortex contains pyramidal cells whose somata occur in layers 2 and 3 and whose dendrites extend radially up to the pial surface. In addition, three populations of neurons occur in both rostral and caudal lateral cortex. Stellate cells occur in all three layers and have dendrites which arborize in all directions. Double pyramidal cells occur primarily in layer 2 and have dendrites which form two conical fields whose long axes are oriented radially. Horizontal cells occur in layer 3 and have dendrites oriented concentric with the ependyma. Fink‐Heimer preparations of snakes which underwent lesions of the main olfactory bulb show that the primary olfactory projections to cortex are bilateral and restricted precisely to rostral lateral cortex. Electron microscopic degeneration experiments indicate that the olfactory bulb fibers end as terminals which have clear, spherical vesicles and asymmetric active zones. The majority are presynaptic to dendritic spines in outer layer 1.These studies establish that lateral cortex in snakes is heterogeneous and contains two major parts, each containing two subdivisions. The rostral and caudal parts have characteristic neuronal populations. Primary olfactory input is restricted to rostral lateral cortex and seems to terminate heavily on the distal dendrites of bowl cells. Axons of some of these cells leave lateral cortex, so that the rostral lateral cortex forms a direct route by which olfactory information reaches other cortical areas. The functional role of caudal lateral cortex is not clear.
Ultrastructural morphology of the shell and shell membrane of eggs of common snapping turtles (Chelydra serpentina)
Authors: Packard Mary J. 
Published: February 2005

AbstractCommon snapping turtles (Chelydra serpentina) lay nearly spherical, flexible‐shelled eggs having an outer mineral layer composed of calcium carbonate in the aragonite form. The mineral layer is arranged into loosely organized groups of nodular shell units, with numerous spaces (or pores) between adjacent shell units. Shell units are structurally complex, consisting of an inner tip that is morphologically distinct from the main body of the shell unit. Contained within an intact shell unit at the interface of the tip and the main part of the shell unit is the central plaque, an apparent modification of the shell membrane that may serve to nucleate calcification of shell units during shell formation. The tips of shell units are firmly attached to a single, multilayered shell membrane throughout much of incubation. The calcareous layer begins to detach from the shell membrane about half‐way through incubation, and changes in shell morphology attending this detachment indicate that snapping turtles may use the shell as a source of calcium during embryogenesis. The arrangement of the mineral layer into groups of shell units, the large number of spaces between shell units, and little or no interlocking of crystallites of adjacent shell units apparently are factors contributing to the ability of these eggs to swell as they absorb water.
Functional morphology of the masticatory musculature of the rodent subfamily microtinae
Authors: Kesner M. H. 
Published: February 2005

AbstractVoles and lemmings are the most successful group of graminivorous rodents, but the adaptations allowing them to enter this niche are not fully known. Dissections of the masticatory musculature of the 12 genera and subgenera of North American microtines show an increase in the potential anterior vector component and in the potential vertical vector component of these muscles relative to the molar tooth row. The result is a separation of the compressive and propulsive functions of the masticatory muscles during the power stroke of mastication. This has led to the formulation of a propalinal “swing” hypothesis which is supported by vector analyses of the musculature.
Intercellular bridges and the fusome in the germ cells of the Cecropia moth
Authors: Mandelbaum Isabel 
Published: February 2005

AbstractIntercellular bridge development was compared in Ceropia by transmission electron microscopy in the germ cells of males and females. Bridge formation begins in the fourth instar, and the spindle remnants in newly formed bridges are replaced at this time by an amorphous material known as the fusome. In the four‐ and eight‐celled cystocyte clusters of the female, the newly formed intercellular bridges migrate centripetally, forming a central complex of bridges surrounded by a rosette of germ cells. The fusomes become continuous and occupy all of the bridges in the complex. At each division each mitotic spindle orients itself with one pole toward the continuous fusome. In the female, mitosis stops at the eight‐cell stage, and the cystocytes all enter first meiotic prophase. At the end of the fifth instar, when nurse cell differentiation commences in seven of the cells, the continuous fusome is replaced by a continuous mass of mitochondria and microtubules. In the male, bridge migration and rosette formation are abandoned during the later mitotic and meiotic divisions; during these stages the fusome is no longer continuous. The fusome of males disappears during spermatid differentiation and is not replaced by mitochondria and microtubules. The ability of the centrally located continuous fusome to orient the mototic spindles of succeeding mitoses could account for the earlier observations that all pre‐existing bridges remain in only one of the daughter cells at each successive cystocyte division in the female.
Ultrastructure of siliceous spicules and microsclerocytes in the marine sponge Neofibularia irata N. SP.
Authors: Wilkinson Clive R. , Garrone Robert 
Published: February 2005

AbstractThe marine sponge Neofibularia irata contains four different categories of siliceous spicules. These spicules are evident in the tissues as distinct bundles that act to increase the structural rigidity of the sponge. All spicules have a normal structural morphology with silica deposition around a hexagonal axial canal containing a crystalline axial filament. The megasclere strongyles are secreted in typical megasclerocytes. The sigma and raphid microscleres are secreted in individual microsclerocytes that are grouped together in parallel to form loose bundles. However, the microxea microscleres are apparently secreted in distinct tight bundles (trichodragmas) within a single cell. These cells, containing between 13 and 39 spicules, are grouped to form large packets of bundles of spicules.
A fine structural study of the testicular wall and spermatogenesis in the crinoid, Florometra serratissima (Echinodermata)
Authors: Bickell Louise R. , Chia Fu‐Shiang , Crawford Bruce J. 
Published: February 2005

AbstractThe testicular wall and the process of spermatogenesis in the crinoid, Florometra serratissima, has been studied at the fine structural level. The testicular wall is composed of three layers: a perivisceral layer consisting of nerve processes, muscle fibers, and epithelial cells; a haemal sinus containing haemal fluid, collagen‐like fibers, and haemocytes; and a germinal layer consisting of germinal and interstitial cells.The germinal layer is elaborated into numerous folds that project into the lumen of the testis and a branch of the haemal channel extends through the core of each fold. Evidence suggesting that nutrients are carried to the testis and germinal cells via the haemal system is presented. Spermatogonia are concentrated around the base of each fold and spermatocytes line the more distal regions. Spermatids occur at the luminal surface of the germinal layer and spermatozoa fill the testicular lumen. Interstitial cells phagocytize spermatozoa and may also transfer nutrients to spermatids.The nucleus of spermatogonia is large and contains one or two nucleoli. The cytoplasm contains numerous organelles, lipid granules, and a distal and proximal centriole, each with a satellite complex. A striated rootlet extends from the distal centriole. During first meiotic prophase, the distal centriole loses its striated rootlet and produces a flagellum, the proximal centriole loses its satellite complex, the nucleolus disappears, and proacrosomal vesicles are synthesized by the Golgi complex. During spermiogenesis, most of the mitochondria appear to fuse to form a single, large mitochondrion, the nuclear chromatin condenses, and superfluous cytoplasm is lost by autophagocytosis. The formation and definitive positioning of the acrosomal vesicle and periacrosomal material at the apex of the nucleus is described in detail.