bluuebunny/crossref_metadata_2025_split huggingface dataset:
Praesomal nerves in Leptorhynchoides thecatus (Acanthocephala: Rhadinorhynchidae)
Authors: Gee Randall J. 
Published: February 2005

AbstractInvestigated by light microscopy, the nerve pathways are described for the first time in the praesoma of a species of Rhadinorhynchidae. The pathways are described for 18 nerves, eight paired and two single, which originate from the cerebral ganglion and a post‐ganglionic cell and terminate in the body wall musculature and the proboscis. The location of three commissures formed by these nerves is also described.
The composite structure of quail pectoralis muscle
Authors: Trotter J. A. , Salgado J. D. , Ozbaysal R. , Gaunt A. S. 
Published: February 2005

AbstractThe twitch fibers of the quail pectoralis muscle were found to have one neuromuscular junction each, located in the middle third of the fiber. The length of isolated fibers varied between 8.8 and 33.2 mm, with mean and median values of 16 and 15.6 mm, respectively. The lengths of the fascicles from which the fibers were isolated varied between 30 and 51 mm. The muscle fibers taper at both ends. The neuromuscular junctions, revealed after histochemically reacting the intact muscle for acetyl cholinesterase activity, were arranged in discrete bands, separated by intervals of between 0.94 and 6.70 mm, with a mean value of 3.14 mm. The quail pectoralis muscle is thus composed of discontinuous, tapered muscle fibers, arranged in an overlapping series. It is therefore a muscle in which tension is transmitted laterally between muscle fibers.
Functional stages in the interrenal cells of Rana perezi (Anura: Ranidae)
Authors: Alvarez Rafael 
Published: February 2005

AbstractThe electron density of the lipid droplets and mitochondrial matrix of the interrenal cells of Rana perezi differs during the year. This makes it possible to characterize the different stages of interrenal cell activity. A droplet/mitochondria index, based on their relative size, may provide an indicator of cellular activity.
Kinematics of the jaw and hyolingual apparatus during feeding in Caiman crocodilus
Authors: Cleuren Johan , de Vree Frits 
Published: February 2005

AbstractMovements of the neck, jaws, and hyolingual apparatus during inertial feeding in Caiman crocodilus were studied by cineradiography. Analysis reveals two kinds of cycles: inertial bites (reposition, kill/crush, and transport) and swallowing cycles. They differ in their gape profile and in displacement of the neck, cranium, and hyolingual apparatus.Inertial bites are initiated by an elevation of the neck and cranium; the head is then retracted backward, the prey simultaneously being lifted by the hyolingual apparatus. Next the lower jaw is depressed, and the prey is rapidly pushed further upward by the hyolingual apparatus. Thereafter fast mouth‐closure occurs with the neck and cranium being abruptly depressed, the lower jaw elevated, and the hyolingual apparatus rapidly retracted ventrally. Depression of the neck and cranium thrusts the head forward and impacts the backward moving prey more posteriorly in the oral cavity.Swallowing cycles initially involve movement of the hyoid in front of the prey followed by rapid posteroventrad retraction of the hyoid, forcing the prey into the esophagus during opening and closing of the mouth. After mouth‐closure, the hyoid apparatus is again protracted.Jaws, neck, tongue, and hyoid apparatus play an active role during intertial feeding sequences. At the beginning of a feeding sequence, the hyolingual apparatus mainly moves dorsoventrally, whereas toward the end of a sequence anteroposterior displacements of the hyoid are prominent. © 1992 Wiley‐Liss, Inc.
Basement membrane lectin binding sites are decreased in the esophageal endoderm during the arrival of presumptive muscle mesenchyme in the developing asteroid Pisaster ochraceus
Authors: Reimer C. L. , Crawford B. J. , Crawford T. J. 
Published: February 2005

AbstractBasement membranes (BMs) of vertebrates and invertebrates have been shown to contain glycoproteins and proteoglycans, which include oligosaccharides and glycosaminoglycans. Lectin binding sites were characterized in the BM of gastrulating embryos of the starfish, Pisaster ochraceus. In early and mid‐gastrulae, the fluorescein isothiocyanate (FITC)‐lectin conjugates of concanavalin A (Con A) and wheat germ agglutinin (WGA) reveal the presence of mannose/glucose and glucosamine/sialic acid residues in the BM of all regions of the embryos. However, in the late gastrula embryo, an apparent reduction of these components is observed over the esophageal BM. Ultrastructural studies using the lectin‐gold conjugates Con A, Limax flavus agglutinin (LFA), specific for sialic acid, and Dolichos biflorus agglutinin (DBA), specific for galactosamine, demonstrate that most mannose/glucose and galactosamine containing residues lie in the lamina densa, whereas most sialic acid residues are located over the lamina lucida. In addition, a statistical analysis of lectin binding in the late gastrula embryo reveals that the amount of labelling with both Con A and LFA is significantly reduced in the esophageal region, suggesting that mannose/glucose and sialic acid residuces are reduced in this region. These results confirm the observations of the FITC‐lectin studies described above. They also confirm earlier studies that demonstrated a difference in BM morphology of the esophageal region (Crawford, '88). Mesenchyme cells, some of which arise from the forming coeloms (Crawford, '90), and which may represent a distinct population, colonize exclusively on this esophageal BM, where they later differentiate into muscle. Quantitative differences in BM glycoconjugates may act to direct the presumptive muscle cells to the region of the esophagus. © 1992 Wiley‐Liss, Inc.
Behavior of postcapillary venule pericytes during postnatal angiogenesis
Authors: Diaz‐Flores Lucio , Gutierrez Ricardo , Varela Hilda 
Published: February 2005

AbstractAutogeneic bone marrow was implanted into an artificially created cavity in a segment of rat sciatic nerve, after removal of nerve fascicles, without damaging the epineurium or surrounding microcirculation. Under these conditions, the bone marrow induces capillary growth and forms granulation tissue from surrounding tissues, the behavior of pericytes being studied in the preformed (preexisting) postcapillary venules of the latter. Beginning 20 h after bone marrow implantation, the pericytes of the preexisting postcapillary venules hypertrophy, with shortening of their processes, prominent nucleoli, dispersal of ribosomes into their free form, fragmentation of basal lamina, and increased DNA synthesis. The number of contact surfaces between pericytes and endothelium is noticeably lower than in controls. Many pericytes are in mitosis. Cells with a shape transitional between pericytes and interstitial fibroblast‐like cells appear. In some cases, Monastral Blue (MB) was used as a marker of the cells in preexisting venule walls of the graft bed. In the earlier stages of the experiment, the MB labelling is restricted to the cytoplasm of pericytes and endothelial cells of postcapillary venules, and to the macrophages that occur in the space between pericytes and endothelium. Furthermore, the marker continues to be observed, at a later stage, in some of the following cells: pericytes and endothelial cells of the newly formed vessels, macrophages migrating into the interstitium, transitional cells between pericytes and fibroblasts, and typical fibroblasts of the granulation tissue. The present study provides greater evidence that preformed microvasculature pericytes are substantially activated during postnatal angiogenesis and granulation tissue formation, suggesting that they may contribute to the origin of new pericytes and fibroblasts. © 1992 Wiley‐Liss, Inc.
Intracytoplasmic ciliary elements in epidermal cells of Syndesmis echinorum and Paravortex cardii (platyhelminthes, dalyellioida)
Authors: Cifrian Blanca , García‐Corrales Pedro , Martínez‐Alos Susana 
Published: February 2005

AbstractEpidermal cells of Syndesmis echinorum and Paravortex cardii contain many intracytoplasmic ciliary components: clusters of centrioles disorganized and incomplete short axonemes composed of loosely organized microtubules of irregular lengths, fully formed axonemes though some with fewer than nine doublets, and ciliary rootlets. Furthermore, conspicuous dense granules are found in solitary groups in the cytoplasm. Clusters of dense granules are also closely associated with Golgi complexes and developing axonemal microtubules. Since the dense granules decrease in number as the axonemes increase, it is likely that the granules are involved in the formation of axonemal microtubules.Ciliary elements are especially abundant in epidermal cells of Paravortex cardii embryos, some of them resembling those previously described by several authors in differentiating ciliated cells engaged in centriologenesis and ciliogenesis. Attention has been focused on the relative proportion and position of these elements, as well as the different morphology and several assembling states that they exhibit in epidermal cells of adult S. echinorum and adults and embryos of P. cardii. A functional interpretation of some of the findings is given, which allows us to suggest a sequence of ciliogenetic events that occur in epidermal cells of both species. © 1992 Wiley‐Liss, Inc.
Natural variation in the limb skeletal pattern of the crested newt, Triturus carnifex (amphibia: Salamandridae)
Authors: Zaffaroni Nicoletta Pacces , Arias Elio , Zavanella Teresa 
Published: February 2005

AbstractThe forelimb skeletal patterns of two geographically isolated populations of Triturus carnifex, one from northern Italy (Rosate, Milano) and one from central Italy (Bagnaia, Perugia) were studied. A total of 1,018 limbs were examined. Limb skeletal variants, generally consisting either of a reduced number of carpals and/or of an alternate phalangeal formula, were commonly observed, as has been reported for other amphibian species. The population from northern Italy showed a greater variability than that from central Italy. Skeletal variants were present in 34% and 12% of the limbs, respectively (i.e., in 48% and 20% of the newts). In the Rosate population, the majority of variants consisted of fusions of radiale and prepollicis and of the phalangeal formula 1‐2‐3‐2. Severe skeletal defects were also found in 3% of the limbs of the newts from Rosate and in 1% of the limbs of those from Bagnaia. At present, no conclusion can be drawn about the evolutionary significance of the limb skeletal variation observed in the two populations, because of the paucity of data on intra‐ and interpopulation variations in other species of the genus Triturus. © 1992 Wiley‐Liss, Inc.
Jaw‐muscle activity in ferrets, Mustela putorius furo
Authors: Dessem Dean , Druzinsky Robert E. 
Published: February 2005

AbstractElectromyographical (EMG) activity was recorded bilaterally from the masseter and temporalis muscles of alert ferrets (Mustela putorius furo) during mastication and crushing. Electromyographic activity was also recorded during biting while a bite‐force transducer placed between the carnassial teeth registered forces ranging from 1.5 to 48.8 N. Linear regression analysis demonstrates that temporalis and masseter EMG activity are linearly related to bite force. Electromyographic activity from the balancing‐side muscles is nearly equal to EMG activity of the working‐side muscles during bone crushing with the carnassial teeth. It is hypothesized that a high percentage of balancing‐side muscle activity in ferrets can be recruited during carnassial biting because the postglenoid process prevents ventral displacement of the working‐side mandibular condyle. © 1992 Wiley‐Liss, Inc.
Neuronal maps of the frontal ganglion of the cockroach, Periplaneta americana, prepared by heavy metal iontophoresis
Authors: Jagota Anita , Habibulla M. 
Published: February 2005

AbstractNeurons in whole mount preparations of the frontal ganglion (FG) of the cockroach, Periplaneta americana, were mapped with the aid of cobalt chloride staining and silver intensification techniques. Eighty‐six neurons were counted in the FG after staining with reduced methylene blue. The cell size ranged between 20 to 35 μm in diameter. Of the somata located in the FG, 44 were found to contribute their fibers to the nervus recurrens, 26 to the right frontal commissure, 28 to the left frontal commissure, and 6 to the nervus connectivus. In addition, a few neurons presumably from the tritocerebral region also contribute their fibers in the formation of nervus connectivus. The present study has helped delineate the neuronal connections of the FG with the brain and neuroendocrine system (corpora cardiaca and corpora allata). This information will be useful in facilitating the positioning of microelectrodes in our future electrophysiological experiments. © 1992 Wiley‐Liss, Inc.
Ultrastructural qualitative and quantitative data on the sporogenesis of the protozoan Abelspora portucalensis (microspora, abelsporidae): A different approach to the study of microsporidia
Authors: Rocha Eduardo , Monteiro Rogério A. F. 
Published: February 2005

AbstractThe sporogenesis of the microsporidium Abelspora portucalensis was studied with electron microscopy. In qualitative terms, new aspects of the cytoplasmic ultrastructure of the schizont, sporont, and sporoblast are described: the presence of microtubules, of aggregates of small opaque vesicles, and of dispersed larger vesicles with clear matrix. The hypothesis that the opaque vesicles may represent the Golgi apparatus and the clear vesicles may correspond to the smooth endoplasmic reticulum is discussed. The use of standard stereological and statistical techniques gives us a new perspective on the development of this microsporidium. The most relevant quantitative data display that the amount of rough endoplasmic reticulum (either in relative or absolute terms) presents significant differences among the three stages, with the sporont showing the highest values; that the absolute (but not the relative) volume of the large vesicles significantly changes during sporogenesis with the highest values presented by the sporont; that the surface‐to‐volume ratio of the schizont and sporont cells is similar and significantly greater than that of the sporoblast cell; that the surface density of the nucleus in relation to soma remains constant in the three stages (on the contrary, the surface‐to‐volume ratio of the nucleus increases and its volumetric density diminishes); and finally, that the nucleolus decreases its relative and absolute volumes. The functional significance of these results is analyzed and the application of similar methodology in quantifying the effects of drugs upon microsporidia is suggested. © 1992 Wiley‐Liss, Inc.
Glomerular development and growth of the renal blood vascular system in Xenopus laevis (Amphibia: Anura: Pipidae) during metamorphic climax
Authors: Ditrich H. , Lametschwandtner A. 
Published: February 2005

AbstractMicrocorrosion casts of the renal vascular system of tadpoles of the Clawed Frog, Xenopus laevis, were observed by scanning electron microscopy. Glomerular differentiation was studied qualitatively and quantitatively during developmental stages 56–66 (metamorphic climax). The general structure of the renal vascular system corresponds to the pattern commonly found in anurans; however, the arterial supply has conspicuous connecting vessels that supply groups of glomeruli. In the dorsal part of the kidney, qualitative differentiation of glomerular structures precedes quantitative growth. The ventral part of the kidney has larger, well‐developed renal corpuscles of nearly adult appearance. Four developmental stages of glomerulogenesis are distinguished morphologically and their glomerular and vascular growth is analyzed. © 1992 Wiley‐Liss, Inc.
The ear in subterranean insectivora and rodentia in comparison with ground‐dwelling representatives. I. Sound conducting system of the middle ear
Authors: Burda Hynek , Bruns Volkmar , Hickman Graham C. 
Published: February 2005

AbstractCompared to acoustically unspecialized mammals (soricids and murids), the middle ear of subterranean insectivores and rodents (twelve species of six families examined) was clearly distinguished and characterized by many common features: rather round and relatively larger eardrum without a pars flaccida; reduced gonial; loose or no connection between the malleus and the tympanic bone; reduced and straightened transversal part of the malleus; enlarged incus; increased and rather flat incudo‐mallear joint; rather parallel position of the mallear manubrium and incudal crus longum in some species (and their fusion in abthyergids); reduced or even missing middle ear muscles. Convergent occurrence of these structural features in taxa of different origin and their generally derived character suggest that they cannot be categorized as degenerative. The form of the stapes can be considered as a non‐adaptive trait; it was taxon specific yet remarkably polymorphous in some species and exhibited no convergent features among subterranean mammals. Structural retrogression resulting in a columella‐like stapes was observed in some species lacking the stapedial artery. The stapedial base was relatively larger than in unspecialized mammals. The subterranean mammals did not exhibit conspicuously enlarged eardrums as would be required for sensitive tuning to low frequencies. It is, however, argued that while selective pressures in the subterranean ecotope promoted hearing of low frequencies, hearing sensitivity did not have to be enhanced. © 1992 Wiley‐Liss, Inc.
The functional morphology of xenarthrous vertebrae in the armadillo Dasypus novemcinctus (Mammalia, Xenarthra)
Authors: Gaudin Timothy J. , Biewener Andrew A. 
Published: February 2005

AbstractIn order to assess the mechanical properties of xenarthrous vertebrae, and to evaluate the role of xenarthrae as fossorial adaptations, in vitro bending tests were performed on posterior thoracic and lumbar vertebral segments excised from specimens of the armadillo Dasypus novemcinctus and the opossum Didelphis virginiana, the latter being used to represent the primitive mammalian condition. The columns of the two species were subjected to dorsal, ventral, and lateral bending, as well as torsion, in order to determine their stiffness in each of these directions. During these tests, bone strains in the centra of selected vertebrae were determined using rosette strain gages. Overall stiffness of the armadillo backbone at physiologically relevant displacement levels was significantly higher than that of the opossum for both dorsal and lateral bending. The two species also exhibited significant differences in angular displacement of individual vertebrae and in vertebral strain magnitudes and orientations in these two directions. No significant differences were observed when the columns of the two species were subjected to torsion or to ventral bending. Our results suggest that some, but not all, of the mechanical differences between the two species are due to the presence of xenarthrae. For example, removal of the xenarthrae from selected vertebrae (L2—L4) changes strain orientation and shear, but not strain magnitudes. Comparisons with functional data from other digging mammals indicate that the modified mechanical properties of the Dasypus column are consistent with an interpretation of xenarthra as digging adaptations and lend support to the idea that the order Xenarthra represents an early offshoot of placental mammals specialized for fossoriality. © 1992 Wiley‐Liss, Inc.
Morphological adaptations of the respiratory hindgut of a marine echiuran worm
Authors: Menon Jaishri G. , Arp Alissa J. 
Published: February 2005

AbstractThe echiuran worm Urechis caupo lives in U‐shaped burrows in marine mudflats where levels of toxic hydrogen sulfide increase and water becomes hypoxic during low tide. Even in this low oxygen and high sulfide environment, the animal is capable of maintaining aerobic respiration. Gas exchange occures across both the body wall and hindgut. The hindgut functions as a type of water lung and is a thin walled, highly convoluted structure capable of considerable dilatation. It is rhythmically ventilated with water and its role as a respiratory organ becomes increasingly important as ambient pO2 drops. In the deflated hindgut light microscopy reveals a pseudostratified appearing innermost mucosal epithelium composed of columnar cells with nuclei at different levels. When the hindgut is fully inflated, ultrastructural studies show a simple columnar epithelium with the nuclei at the same level. Ultrastructurally, the free surface of the hindgut cells bears numerous microvilli and a few cilia. The lateral cell membranes are highly folded in the deflated hindgut, but these folds are not visible in the fully inflated hindgut. The cytoplasm contains osmiophilic bodies which show a partially lamellated pattern which may be sulfide oxidizing bodies involved in sulfide detoxification. In the fully inflated hindgut, the entire perimeter of the lumenal mucosa is covered by electron dense inclusions, whose exact fuction is unknown. The lack of structural information on the respiratory organ of this echiuran worm renders the interpretation of its morphological and histological features at the ultrastructural level difficult, although the present study has broadened our understanding of the structural adaptations of the hindgut as a respiratory organ. © 1992 Wiley‐Liss, Inc.
Stereotaxic atlas of the brain of Octodon degus
Authors: Wright John W. , Kern Michael D. 
Published: February 2005

AbstractWe present a stereotaxic atlas of the brain of the trumpet‐tailed rat or degu (Octodon degus), an hystricomorph rodent native to Chile and one which has become increasingly popular as a research animal, among other things because of its use as a model for diabetic catarcts and its tendency to become hyperglycemic. The atlas contains 38 transverse and two sagittal sections of the brain covering pros‐, mes‐, and rhombencephalon, as well as diagrams of the brain's surface anatomy. It was constructed from brains of young adult male degus but can be used readily in studies of adult females, since there is no apparent sexual dimorphism in the brain size of this rodent. Ninety percent of 40 experimental lesions used to check the accuracy of the atlas were correctly placed.The fore‐ and midbrain of the degu are generally more compact than corresponding regions of the brain in the laboratory rat (suborder Myomorpha) and the guinea pig (another hystricomorph). The amygdaloid complex extends further forward in the telencephalon. Major mesencephalic nuclei and fiber tracts are more rostral in position. However, superior and inferior colliculi are much longer in degus than rats. The basic organization of the rhombencephalon is similar in degus and rats, although there are clearcut differences in the length or size of some hindbrain nuclei. © 1992 Wiley‐Liss, Inc.