bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus)
Authors: Byrd Kenneth E. 
Published: February 2005

AbstractOptoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the durations of EMG activity between the working and balancing side during all three cycle types. High level activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a „braking”︁ or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.
Morphological and ultrastructural aspects of Branchiobdella pentodonta Whit. (Annelida, oligochaeta) suckers
Authors: Farnesi Rosalba M. , Marinelli Marinella , Tei Simonetta , Vagnetti Daniela 
Published: February 2005

AbstractThe muscular system in the posterior sucker of Branchiobdella pentodonta Whit. has circular, longitudinal and radial fibers. In the anterior sucker, which has circular and longitudinal fibers, the muscle system is scarce. Concentric fibers are found around the mouth. In both suckers the glandular elements form voluminous complexes secreting mucus for attachment to the substrate. Suckers show neuromuscular junctions and three distinct types of neuroglandular junctions: one with typical neurosecretory granules, one with larger neurosecretory granules produced by cells located at the origin of the segmental nerves, and one with presynaptic vesicles. The second type is peculiar to the posterior sucker. A comparison is made between suckers of Branchiobdella and those of leeches.
Ultrastructure of the heart of the marine mussel, Geukensia demissa
Authors: Watts John A. , Koch Robert A. , Greenberg Michael J. , Pierce Sidney K. 
Published: February 2005

AbstractThe structure of the heart of Geukensia demissa, a common object of physiological and biochemical investigation, is described by scanning, transmission and freeze‐fracture electron microscopy. A single‐cell epithelial layer covers the ventricle, but an endothelium is lacking. Myofibers are small (6–7 μm diam.), mononucleate, and tapered. Glycogen is concentrated peripherally. Mitochondria are particularly concentrated under the sarcolemma, near the ends of the nucleus, and in rows between bundles of myofilaments. The myofilaments (6–8nm thin, 30–35 nm thick filament diam.) are loosely arranged into sarcomeres (2–4 μm) by Z bodies. Many of these Z bodies interconnect, and some anchor to the sarcolemma forming attachment plaques. Cells are joined by intercalated discs consisting of fascia adherentes, spot desmosomes, and gap junctions. The gap junctions include intramembrane particles. T tubules are absent. The sarcolemma is coupled to the junctional sarcoplasmic reticulum (JSR) over 357ndash;40% of the cell surface. Tubules extend from the JSR deep into and throughout the cell as an irregularly dispersed network. The SR occupies 1% of the cell volume. A few, small (0.1–1.0 μm) unmyelinated nerves are present, but no neuromuscular junctions were seen. The auricles have fewer and smaller myocytes than the ventricle. The auricles also contain podocytes with pedicels having 20–35 nm slits and containing sieve‐like projections. The morphology of the Geukensia heart is similar to that of other bivalves.
Foot of two‐toed sloths: Its anatomy and potential uses relative to size of support
Authors: Mendel Frank C. 
Published: February 2005

AbstractFeet of two‐toed sloths (Choloepus) are long, narrow, hook‐like appendages with only three functional digits, numbers II, III, and IV; Rays I and V are represented by metatarsals. Proximal phalanges of complete digits are little more than proximal and distal articulating surfaces. All interphalangeal joints are restricted, by interlocking surfaces, to flexion and extension. Ankle and transverse tarsal joints, however, allow extreme flexion and inversion of foot. Powerful digital flexion is augmented by several muscles from extensor compartment of leg. Intrinsic foot musculature is reduced to flexors and extensors but these, with the exception of lumbricals, are large and well developed. Choloepus uses its feet much like hooks with distal phalanges and covering claws forming the “hook” element. These hook‐like appendages are seemingly best suited for supports less than 50 mm in diameter suggesting that two‐toed sloths may prefer supports of this size in their natural habitat.
Ultrastructural localization of glucose‐6‐phosphatase and alkaline phosphatase in the vaginal epithelium of rat
Authors: Kang Yuan‐Hsu , West William L. 
Published: February 2005

AbstractThe effect of ovarian hormones on the activities of glucose‐6‐phosphatase and alkaline phosphatase in the vaginal epithelium was studied in immature and ovariectomized rats, using ultracytochemical techniques. Comparative studies were done on normal rats at the luteal phase and on day 14 of pregnancy.Various vaginal cells show different degrees of response to progesterone and diethylstilbestrol (DES) with regard to glucose‐6‐phosphatase activity. Intense glucose‐6‐phosphatase activity was observed in the cisternae of granular endoplasmic reticulum (rER), Golgi saccules and vesicles, and nuclear envelope of both basal cells and stromal cells of progesterone treated rats, whereas in the basal cells and stromal cells of DES‐treated and control animals the enzyme was totally lacking. Detectable glucose‐6‐phosphatase activity was also observed, however, in the rER cisternae and Golgic complex of keratohyalin‐secreting squamous intermediate cells of the vaginal epithelium of DES‐treated rats. Alkaline phosphatase was observed in the plasma membranes of various cell types of vaginal epithelium in the normal, progesterone‐, and DES‐treated rats, Alkaline phosphatase was also found on the limiting membranes of secretory granules of mucocytes in animals at the luteal phase and during pregnancy. DES and progesterone in the doses used did not affect alkaline phosphatase activity in the rat vagina. Overall, progesterone enhances glucose‐6‐phosphatase activity in basal cells of the rat vagina prior to completion of mucification. Alkaline phosphatase was found in all cells involved in mucin secretion.
Rosette glands in the gills of the grass shrimp, Palaemonetes pugio. I. Comparative morphology, cyclical activity, and innervation
Authors: Doughtie Daniel G. , Rao K. Ranga 
Published: February 2005

AbstractTwo types of exocrine rosette glands (called type A and type B), located in the gill axes of the grass shrimp Palaemonetes pugio, are described. The type A glands are embedded within the longitudinal median septum of the gill axes, whereas the type B glands typically project into the efferent hemolymph channels of the gill axes. Although both glands have certain common characteristics (i.e., a variable number of radially arranged secretory cells, a central intercalary cell, and a canal cell that forms the cuticular ductule leading to the branchial surface), they differ in the following respects. The type B gland is innervated, but the type A gland is not; axonal processes, containing both granular (ca. 900–1300 Å) and agranular (ca. 450–640 Å) vesicles, occur at a juncture between adjacent secretory cells and the central cell of the type B gland. The secretory cells of type A and type B glands differ in their synthetic potential and membrane specializations. These differences are more pronounced in well‐developed, mature glands, most frequently encountered in larger (24–28 mm, total length) grass shrimp, than in the underdeveloped, immature glands that are most abundant in smaller (14–18 mm, total length) grass shrimp. Thus, in mature glands, the secretory cells of the type A rosette glands are characterized by extensive RER, abundant Golgi, and numerous secretory granules, whereas the secretory cells of the type B gland are characterized by extensively infolded and interdigitated basal plasmalemmas and by the presence of numerous mitochondria. In general, both types of glands exhibit increased secretory activity soon after ecdysis. The central and canal cells in both glands seem to have a role in the modification of the secreted materials. The possible functions assigned to the type A gland and the type B gland include phenol‐oxidase secretion and osmoregulation, respectively.
Two sperm types in the spermatozeugmata of Tubifex tubifex (annelida, oligochaeta)
Authors: Braidotti Paola , Ferraguti Marco 
Published: February 2005

AbstractThe spermatozeugmata (sperm bundles lacking a distinct wall) from the spermathecae of Tubifex tubifex are composed of two different zones: an internal axial cylinder containing conventional spermatozoa and an external cortex composed of modified spermatozoa, tightly packed together. The conventional spermatozoa conform to the classical clitellate scheme: very long and thin with a complex acrosome, a filiform nucleus, small mitochondria, and a flagellum with Y links and β glycogen granules as accessory structures. The modified spermatozoa show “empty” acrosomes, degenerating nuclei, and tails which contain γ glycogen granules. The tails are helically wound around the spermatozeugma and are connected to each other by junctional complexes. The tips of the cortical tails are free and move with a metachronal wave. The presence of two sperm types in tubificids is discussed and a protective function for the modified cortical spermatozoa is proposed.
Morphometric studies on tenuissimus muscle spindles in the cat
Authors: Kucera Jan 
Published: February 2005

AbstractMuscle spindles were studied histochemically in serial transverse sections of 42 cat tenussimus muscle specimens. Staining for myofibrillar adenosine triphosphatase was employed to identify nuclear bag1, nuclear bag2, and nuclear chain intrafusal muscle fibers. The nuclear chain fibers were further subdivided into three categories according to their polar length and the intensity of their staining for nicotinamide adenine dinucleotide tetrazolium reductase. A total of 430 spindle poles were surveyed. The mean spindle content of bag1, bag2, and chain fibers was established. The mean polar length of intrafusal fibers as well as that of the intracapsular and extracapsular spindle regions was determined. A cholinesterase (ChE) staining technique was used to demonstrate the termination sites of motor axons along intrafusal fibers. Two types of circumscribed ChE deposits, the “rim” and the “plate,” occurred on the fibers. The nuclear chain fibers usually carried both the ChE rims and plates, while most nuclear bag fibers displayed only the plates. The ChE plates were assessed in term of their appearance, staining intensity, length, and location along the fibers. The mean number of ChE plates found along the fibers was established for each of the various intrafusal fiber types.These histochemical observations are discussed with regard to the current concepts of cat spindle morphology and motor innervation. The results suggest a degree of predictability in the spindle fiber content and in the distribution of motor nerve terminals along intrafusal muscle fibers, at least in the tenuissimus muscle.
The organization of the octavolateralis area in actinopterygian fishes: A new interpretation
Authors: McCormick Catherine A. 
Published: February 2005

AbstractThe octavolateralis area of actinopterygian fishes can be subdivided into a dorsal lateralis area composed of first‐order lateral line nuclei, and a ventral octavus area composed of nuclei receiving first‐order input from the eighth nerve. Three patterns of organization of the lateralis area are recognized in the present study. The organization of this area in polypteriforms and chondrosteans is similar to that in chondrichthyans. On the basis of recent studies in chondrichthyans (McCready and Boord, '76; Boord and Campbell, '77; Bodznick and Northcutt, '80), it is hypothesized that this pattern reflects the subdivision of the lateral line system into mechanoreceptive and electroreceptive portions. As petromyzontid agnathans also share this pattern of organization, it is hypothesized that they are elecroreceptive. The lateralis area of holosteans and nonelectroreceptive teleosts exhibits a second organizational pattern that is hypothesized to reflect the loss of the electroreceptive portion of the lateral line system; it is suggested that electroreception was lost sometime between the chondrostean and teleostean radiations. Each group of electroreceptive teleosts is believed to have evolved electroreception independently (Bullock, '74), a situation that is reflected centrally by a third organizational pattern within the lateralis area, which is distinctly different from that of early radiations of electroreceptive fishes.The octavus area of actinopterygians exhibits two patterns of organization–that of polypteriforms, chondrosteans, and holosteans, and that of teleosts. The functional significance of these patterns has yet to be elucidated.
Development of the embryonic chick phagocytic system: Intraembryonic erythrophagocytosis induced by phenylhydrazine
Authors: Sorrell J. Michael , Weiss Leon 
Published: February 2005

AbstractThe intraembryonic reticuloendothelial response to phenylhydrazine‐induced hemolytic anemia was studied embryonic chicks (days 13–16) by light and electron microscopy and histochemical and biochemical assays for acid phosphatase. Phenylhydrazine was given on day 13 and tissue taken at 2, 5, and 10 h and at 1, 2, and 3 days after injections. The response varied in the three major reticuloendothelial organs. The spleen first demonstrated an increase in erythrophagocytosis that was accompanied by increased acid phosphatase levels. Erythrophagocytosis occurred primarily in the red pulp resulting in increased numbers of macrophages, increased size of macrophages, and retention of erythrocytes, which together combined to enlarge the spleens. By 2 days after phenylhydrazine injection, greatly enlarged macrophages began to migrate into the venous system, where some erythrophagocytosis continued to occur. The liver was also a major erythroclastic organ in which Kupffer cells became increasingly erythrophagocytic. However, erythrophagocytosis began later than in the spleen, and as measured by acid phosphatase levels, the liver was not as effective in removing damaged erythroid cells. Marrow erythrophagocytosis was only slightly enhanced; however, the marrow responded by increasing its production of red blood cells. Thus, the intraembryonic reticuloendothelial organs of the embryonic chick responded to phenylhydrazine‐induced hemolytic anemia in much the same manner as might be expected of the adult bird.
Innervation and structure of mouth part sensilla in females of the black fly Simulium venustum (Diptera: Simuliidae)
Authors: Sutcliffe James F. , McIver Susan B. 
Published: February 2005

AbstractAssociated with the mouth parts of female Simulium venustum are 13 morphologic types of sensilla: four on the labium, seven on the labrum, one in the cibarium, and one on the genal process to which the mandibles articulate. Seven types are probably sensitive only to mechanicla cues and three only to chemical ones, whereas the other three probably function in both modes. These sensilla likely monitor feeding‐associated chemical features of blood, sugar, and water and mechanical cues generated by the physical acts of ingestion.Each S. venustum female has approximately 450 chemosensitive and 230 mechanosensitive neurons in the mouthpart‐associated sensilla. Both the total number of chemosensory neurons and the ratio of chemosensory to mechanosensory neurons in S. venustum are intermediate between those for blow flies, which feed on a wide variety of foodstuffs, and tsetse flies, exclusive blood‐feeders. These differences may be related to whether determination of acceptability of a potential food source occurs at the site of feeding and is dependent upon simultaneous sensitivity to many chemical cues, as in blow flies, or is the result of a complex stimulus chain composed of all host‐location steps and culminating with the detection of but a few phagostimulants in the food itself, as in blood‐feeders.
Morphology of the aedeagal gland of the male mealworm beetle (Tenebrio molitor L.)
Authors: Dailey Patrick J. , Happ George M. 
Published: February 2005

AbstractThe aedeagal gland of male Tenebrio molitor consists of numerous acini containing several secretory units (organules) of three epithelial cells in series. The distal cortical cell and intermediate cell are secretory cells. Secretory products are passed into microvilli‐lined extracellular reservoirs. From these storage areas products flow through minute canaliculi and into the efferent ductule. Canaliculi, cuticular trabeculae, and fibrillar material are characteristic features of the efferent ductules within the extracellular reservoirs of secretory cells. After passing from the secretory cells, the efferent ductule penetrates the basal ductule cell. The thin epicuticle that comprises the wall of the ductule is confluent with the epicuticle of the cuticular sheath forming the wall of the genital pocket. Secretory products flow from the cortical cell ductule into the intermediate cell and eventually empty into the genital pocket. A chemical reaction apparently takes place in the intermediate cell ductule, resulting in a frothy secretion product. When released from the ductule, this frothy product forms a foam‐like layer that coats the inner wall of the genital pocket. Ultrastructural and probable functional aspects of this gland are described and discussed.
Structure and evolution of tetraodontoid teeth: An autoradiographic study (pisces, Tetraodontiformes)
Authors: Andreucci Roberto D. , Britski Heraldo A. , Carneiro José 
Published: February 2005

AbstractFor years teeth of tetraodontoid fishes generally have been considered coalescent even though “coalescence,” which also is found in fishes of other families, has never been well defined. This paper deals with some aspects of coalescence of the teeth in tetraodontoids and attempts to define this condition. The sites of osteodentinogenesis and the mechanisms by which hard tissues are formed, reabsorbed, and abraded during feeding were analyzed from semiserial decalcified sections and from ground sections, as well as from autoradiographs of the premaxilla and dentary bones of Sphoeroides greeleyi. The observations reported here, taken together with other data we have obtained on members of the Tetraodontoidei, permit clear definitions of “tooth” and “supporting bone,” and consequently the structural meaning of coalescence. From these data we hypothesize how coalesced masticatory structures may have evolved in this group.
Fine structure of maxillary sensilla of larval Toxorhynchites brevipalpis (Diptera: Culicidae) with comments on the role of sensilla in behavior
Authors: McIver Susan , Siemicki Roman 
Published: February 2005

AbstractEach maxilla of fourth instar Toxorhynchites brevipalpis bears nine sensilla: Four are located at the tip of the maxillary palp and five on the maxillary body. At the palp tip are three tapered pegs on bulbous bases (MS1, MS2, MS6) that are innervated by four, two, and two neurons, respectively, and probably function in chemoreception. Also at the palp tip is a sturdy, cuticular rod with a lumen (MS5) that opens distally to the exterior. The proximal end of the rod is closed by a cuticular base to which a single unbranched dendrite containing only a few microtubules is attached. The function of MS5 is enigmatic; possibilities include mechanoreception and detection of infrared radiation.On the maxillary body are two tapered pegs on a common bulbous base (GS1, GS2) that are each innervated by three neurons, and probably are chemosensory. Three setae also occur on the maxillary body. They arise from prominent sockets and are each innervated by a neuron terminating at the hair base as a tubular body, a characteristic of cuticular mechanosensilla.The maxillary sensilla are innervated by a total of 18 neurons: 14 are probably chemosensory, three mechanosensory, and one is of unknown function. These results, combined with those from a previous study on antennal sensilla (Jez and McIver, '80), indicate that the mechanosensitive neurons of the antennae and maxillae are a relatively small percentage of the total mechanosensilla on the entire larva. In contrast the chemosensitive neurons of the antennae and maxillae provide most of the information about the chemical environment of the larva.T. brevipalpis has three less than the maximum of seven maxillary palpal sensilla found in larval mosquitoes so far studied. This difference may reflect a lesser need for sensory information about the acceptability of potential food in predators compared to browsers and filter‐feeders.
Intraendodermal and intramesenteric migration of anuran amphibian germ cells: Transmission and scanning electron microscopy
Authors: Delbos Martine , Gipouloux Jean‐Daniel , Guennoun Samira 
Published: February 2005

AbstractPrimordial germ cells (PGCs) from the dorsal side of midgut endoderm and from within the dorsal mesentery were examined by transmission and scanning electron microscopy. During migration of these cells, lamellipodia and filopodia, develop in a polarized pattern. Large amounts of extracellular material accumulate around the lamellipodia at the leading end of a migrating cell. It is suggested that the polarized pseudopodia function in conjunction with extracellular matrix as the means by which PGCs move en route to gonadal ridges.