bluuebunny/crossref_metadata_2025_split huggingface dataset:
The organization of the reptilian brainstem reticular formation: A comparative study using Nissl and Golgi techniques
Authors: Newman Donald B. , Cruce William L. R. 
Published: February 2005

AbstractThe brainstem reticular formation has been studied in 16 genera representing 11 families of reptiles. Measurements of Nissl‐stained reticular neurons revealed that they are distributed along a continuum, ranging in length from 10 μm to 95 μm. Reticular neurons in crocodilians and snakes tend to be larger than those found in lizards and turtles. Golgi studies revealed that reticular neurons posess long, rectilinear, sparsely branching dendrites. Small reticular neurons ( > 31 μm length) possess fusiform or triangular somata which bear two or three primary dendrites. These dendrites have a somewhat simpler ramification pattern when compared with those of large reticular neurons (< 30 μm length). Large reticular neurons generally possess perikarya which are triangular or polygonal in shape. The somata of large reticular neurons bear an average of four primary dendrites. The dendrites of reptilian reticular neurons ramify predominantly in the transverse plane and are devoid of spines or excrescences. The dendritic ramification patterns observed in the various repitilian reticular nuclei were correlated with known input and output connections of these nuclei.Nissl and Golgi techniques were used to divide the reticular formation into seven nuclei. A nucleus reticularis inferior (RI) is found in the myelencephalon, a reticularis medius (RM) in the caudal two‐thirds of the metencephalon, and a reticularis superior (RS) in the rostral metencephalon and caudal mesencephalon. Reticularis inferior can be subdivided into a dorsal portion (RID) and a ventral portion (RIV). All reptilian groups possess RID and RM but RIV is lacking in turtles. Reticularis superior can be subdivided into a large‐celled lateral portion (RSL) and a small‐celled medial portion (RSM). All reptilian groups possess RSM and RSL, but RSL is quite variable in appearance, being best developed in snakes and crocodilians. The myelencephalic raphe nucleus is also quite variable in its morphology among the different reptilian families. A seventh reticular nucleus, reticularis ventrolateralis (RVL), is found only in snakes and in teiid lizards. It was noted that the reticular formation is simpler (fewer numbers of nuclei) in the representatives of older reptilian lineages and more complex (greater numbers of nuclei) in the more modern lineages. Certain reticular nuclei are present or more extensive in those families which have prominent axial musculature.
Appendicular skeletal morphology in minute salamanders, genus Thorius (amphibia: Plethodontidae): Growth regulation, adult size determination, and natural variation
Authors: Hanken James 
Published: February 2005

AbstractPatterns of growth and variation of the appendicular skeleton were examined in Thorius, a speciose genus of minute terrestrial plethodontid salamanders from southern Mexico. Observations were based primarily on ontogenetic series of each of five species that collectively span the range of adult body size in the genus; samples of adults of each of seven additional species provided supplemental estimates of the full range of variation of limb skeletal morphology.Limbs are generally reduced, i.e., pedomorphic, in both overall size and development, and they are characterized by a pattern of extreme variation in the composition of the limb skeleton, especially mesopodial elements, both within and between species. Fifteen different combinations of fused carpal or tarsal elements are variably present in the genus, producing at least 18 different overall carpal or tarsal arrangements, many of which occur in no other plethodontid genus. As many as four carpal or tarsal arrangements were observed in single population samples of each of several; five tarsal arrangements were observed in one population of T. minutissimus. Left‐right asymmetry of mesopodial arrangement in a given specimen is also common.In contrast, several unique, nonpedomorphic features of the limb skeleton, including ossification of the typically cartilaginous adult mesopodial elements and ontogenetic increase in the degree of ossification of long bones, are characteristic of all species and distinguish Thorius from most related genera. They form part of a mechanism of determinate skeletal growth that restricts skeletal growth after sexual maturity. Interspecific differences in the timing of the processes of appendicular skeletal maturation relative to body size are well correlated with interspecific differences in mean adult size and size at sexual maturity, suggesting that shifts in the timing of skeletal maturation provide a mechanism of achieving adult size differentiation among species.Processes of skeletal maturation that confer determinate skeletal growth in Thorius are analogous to those typical of most amniotes – both groups exhibit ontogenetic reduction and eventual disappearance of the complex of stratified layers of proliferating and maturing cartilage in long bone epiphyses – but, unlike most amniotes, Thorius lacks secondary ossification centers. Thus, the presence of secondary ossification centers cannot be used as a criterion for establishing determinate skeletal growth in all vertebrates.
Synthesis of the vitelline and chorionic membranes of an ichneumonid parasitoid
Authors: Norton William N. , Vinson S. Bradleigh 
Published: February 2005

AbstractA reduction in free ribosomes and increases in rough endoplasmic reticulum and Golgi complexes in follicle cells during oogenesis suggest their involvement in supplying precursor material for synthesis of the vitelline and chorionic membranes of the ichneumonid parasitoid Campoletis sonorensis. The inner region of the vitelline membrane is composed of a narrow band of electron‐opaque material; an outer region adjacent to the chorion consists of overlapping, irregularly shaped laminae. The fully developed chorion can be divided morphologically into three distinct regions. Its inner region adjacent to the lamellar plates of the vitelline membrane is composed of a lamellar membrane exhibiting a regular periodicity of crossbands. The middle section is composed of longitudinal chambers, some of which contain particulate matter. The outer region consists of slender projections which extend perpendicularly from the chorion surface. A fine layer of fibrous material adheres to the projections. The possibility of a relationship between the presence of fibrous material on the surface of parasitoid eggs and the inactivation or inhibition of host immune systems is mentioned.
Structure of the shell from eggs of the tuatara, Sphenodon punctatus
Authors: Packard Mary J. , Hirsch Karl F. , Meyer‐Rochow V. B. 
Published: February 2005

AbstractShells from eggs of the tuatara (Sphenodon punctatus) are 0.2 mm thick and are composed of a layer of calcite and a multi‐layered, fibrous shell membrane. Most of the calcareous layer is composed of roughly circular columns of crystalline material that extend deep into the shell membrane. The crystalline matrix of the columns is interwoven with fibers of the shell membrane except near the outer surface of the eggshell, where the calcareous material is more compact. Overlying the columns is a granular layer composed of blocks of crystalline material of random size, shape, and orientation. Disruption of this granular layer, perhaps through swelling of the eggs or as a result of environmental factors, gives the outer surface of the eggshell a coarse, weathered appearance. Removal of the calcareous material with a decalcifying agent shows that the outer surface of the shell membrane is composed of a meshwork of small fibers bound together by an amorphous matrix. No matrix was observed in inner layers of the shell membrane, and the fibers of these inner layers are arranged somewhat more regularly than the outer fibers. No structure comparable to the central cores of avian and certain chelonian eggs was observed in eggshells of the tuatara.
Electromyography of the opercularis muscle of Rana catesbeiana: An amphibian tonic muscle
Authors: Hetherington Thomas E. , Lombard R. Eric 
Published: February 2005

AbstractThe opercularis muscle of Rana catesbeiana originates on the suprascapular cartilage of the shoulder girdle and inserts on the otic opercular element. It is part of the levator scapulae musculature and lies dorsomedial to the levator scapulae superior and inferior muscles. Bipolar electrode recordings from all three muscles show electrical activity linked to cyclical firing of the posterior intermandibularis muscle, an important ventilatory muscle. The opercularis muscle shows low amplitude, erratic signals when animals are sumerged. Upon emergence of the snout region, the opercularis muscle shows rhythmic low amplitude activity at twice the rate of buccal pumping. Lung ventilation is synchronized with this rhythm and at ventilation the opercularis muscle shows higher amplitude activity. Upon submergence, opercularis activity again shows low level activity with no rhythmic pattern. Opercularis muscle activity has a major low frequency component (about 30 Hz) that probably corresponds to activity of tonic muscle fibers. Higher frequency signals (about 200–250 Hz) comparable to those of the levator scapulae muscles are also present and probably represent activity of phasic muscle fibers. Activity of the opercularis muscle is correlated with conditions in which aerial respiration is possible, and this pattern of activity supports an opercularis role in aerial hearing and/or detection of substrate vibrations. As far as we know, this is the first report of electromyographic analysis of a vertebrate tonic muscle.
Terminal airway embryology of the delphinid porpoises, Stenella attenuata and S. longirostris
Authors: Drabek Charles M. , Kooyman Gerald L. 
Published: February 2005

AbstractA light microscopic investigation of the histological development of the terminal airways of 18 Stenella attenuata and two S. longirostris showed the lungs to be in a glandular stage of development until 3 months postimplantation (p.i.) age. By 3.5 months (p.i.) the lung was at the canalicular stage. At 4 months mesenchymal rings and muscular bands were in a sphincterlike arrangement around terminal bronchioles. At 7 months (p.i.) the alveolar stage occured. About 8–9 months cartilaginous rings were present and in association with myoelastic sphincters. Their function remains an enigma, even though many hypotheses as to function have been proposed. We suggest that the presence of well‐developed sphincters and cartilage in the neonate may give clues to their function as well as offer potential experiments that would not be as suitable in the adult porpoise.
Ultrastructure of the tubular nephron of the lizard Podarcis (= Lacerta) Taurica
Authors: Gabri M. S. 
Published: February 2005

AbstractThe proximal, intermediate, and distal convoluted tubules of the neprhon of Podarcis (= Lacerta) taurica were examined by electron microscopy. Proximal tubule cells have large, apical cytoplasmic protrusions and microvilli interpreted to function in urate secretion. Adjacent cells are bound apically by tight junctions and desmosomes but interdigitate in their basal region. This situation is repeated in the other tubules with significant differences in intercellular space width. The basal surfaces bear numerous cytoplasmic processes. The intermediate tubule has proximal and distal segments each with dark, ciliated, and light cells, the cuboidal dark cells with dense cytoplasm constituting the main bulk of the wall. As the cells of the proximal and distal segments resemble those of the proximal and distal convoluted tubules, respectively, the intermediate tubule is considered as a transition region. The ciliated cell body has two broad processes extending from the lumen, one to the basement membrane and one to a foot process of a light cell. The light cell is surrounded by dark and ciliated cells. It does not reach the lumen, but contacts the basement membrane through a process running below a ciliated cell to form a mushroom‐shaped structure in tubule cross‐section, the light cell process forming the stalk and a ciliated cell the cap. The cilia probably propel the glomerular filtrate towards the distal convoluted tubule. This latter tubule has initial, middle, and terminal zones, all nonciliated but with different lumen widths and cell shapes.
Histochemical and ultrastructural features of the epidermis of the land planarian Bipalium adventitium
Authors: Curtis Sherill K. , Cowden Ronald R. , Moore J. D. , Robertson J. Leonard 
Published: February 2005

AbstractThe epidermis of the land planarian Bipalium adventitium was examined by light and electron microscopy. In all regions, the epidermis consists of a simple columnar ciliated epithelium associated with a prominent basement membrane. The epithelial cells, possessing abundant microvilli and poorly developed terminal webs, are conjoined laterally at their apical ends by septate junctions. The epidermis of the creeping sole is distinguished from that of adjoining regions by a “insunken” condition of the epithelial cells, a greater number of cilia per cell, and an absence of glandular secretions other than mucus. The insunken cells of the sole possess large glycogen disposits and attributes of metabolically active cells. Unusual intranuclear inclusions of unknown significance are also found in many of the epidermal cells in all regions. The basement membrane lacks distinct layering and consists of fine fibrils displaying a beaded appearance but no obvious cross‐banding. Histochemical tests indicate that the fibrils are collagenous. In addition to mucus, secretory material found in nonsole regions includes lamellated granules and rhabdites, both stained intensely by acidic dyes. Rhabdites and the basement membrane also contain disulfide‐enriched proteins. In scanning electron micrographs, the sole appears as a faint, longitudinally oriented band extending along the entire length of the animal. In all regions except the sensory border of the head, the microvilli are generally obscured by the densely arranged cilia. The sensory border consists of a row of toothlike papillae and grooves covered almost exclusively by microvilli, small club‐shaped structures, and larger spherical protrusions.
The sensory systems and feeding behavior of leafhoppers. II. A comparison of the sensillar morphologies of several species (Homoptera: Cicadellidae)
Authors: Backus Elaine A. , McLean Donald L. 
Published: February 2005

AbstractThe ultrastructure of the sensilla, and other structures, within the precibaria of eight species from three subfamilies of leafhoppers (Homoptera: Cicadellidae) were examined with scanning electron microscopy. The types and grouping of the 20 precibarial sensilla in seven of these species were similar to those observed previously in Macrosteles fascifrons Stål. Oncometopia nigricans (Walker) also displayed similar sensilla groups; however, it had 30 sensilla. The species examined differed chiefly in the exact location and arrangement of the sensilla. The possible significance of the differences relative to leafhopper feeding is discussed. The precibarial chemosensilla may provide chemosensory evaluation of fluid in the food canal and precibarium prior to ingestion or egestion.
Early ontogeny of the annual fish genus Nothobranchius: Cleavage plane orientation and epiboly
Authors: van Haarlem Robert 
Published: February 2005

AbstractLiving embryos of ten species of the teleost fish Nothobranchius were observed from fertilization through the ten‐somite stage. Cellular behaviour during early development showed differences as well as similarities among species. In one species at the eight‐cell stage the blastomeres are arranged in two rows of four cells, all in one plane. In three other species the blastomeres are arranged in two layers of four cells, each one above the other, and in the remaining six species the arrangement is intermediate between the one‐layer and two‐layer pattern. Hybridization experiments showed that the sequence of orientation of cleavage planes is not under the control of either the nucleus or of cytoplasmic factors from the sperm. At midcleavage stages, marginal cells of the blastoderm undergo fusion, thus giving rise to the external‐Yolk Syncytial Layer. A second period of fusion of cells of the Enveloping Layer occurs just before epiboly starts and a third one after epiboly has concluded. Marginal cells of the Enveloping Layer do not possess cell protrusions such as blebs, lobopodia, or filopodia; therefore, spreading of the Enveloping Layer during epiboly by means of locomotion of marginal cells seems unlikely. Evidence is presented that the deep cells within the segmentation cavity remain separated from one another through contact inhibition during epiboly and that they use the Enveloping Layer as a substratum during their dispersion over the yolk. A description of normal stages applicable to all ten species of Nothobranchius is presented.
Cleavage in vivo and in culture in the dasyurid marsupial Antechinus stuartii (macleay)
Authors: Selwood Lynne , Young G. J. 
Published: February 2005

AbstractCleavage in the brown marsupial mouse, Antechinus stuartii, from the zygote to the unilaminar blastocyst, was observed in vivo and in culture and in sections of embryos. The first three divisions were meridional and passed from the yolk pole to the opposite pole. Deutoplasmolysis, resulting in a distinct yolk mass, occurred during the first two divisions. Prior to the third and fourth divisions, the blastomeres elongated and flattened against the zona pellucida. The fourth division was latitudinal and resulted in two histologically distinct rings of eight blastomeres which were at first rounded and then became flattened against the zona. Further divisions and flattening of the blastomeres resulted in a complete unilaminar blastocyst by the time the blastocyst numbered 22 to 30 cells. Some expansion, causing compression of the zona and mucoid layers, occurred before completion of the blastocyst, but most expansion occurred once the blastocyst was complete. No histological differences could be detected between the blastomeres at this stage. Embryos were successfully cultured from the zygote to the rounded four‐cell stage and from the flattened four‐cell stage to the completed unilaminar blastocyst of around 32 cells. Total estimated cleavage times were slower in culture than in vivo, but the relative lengths of time for each division were approximately the same.
A correlated light and electron microscopic study of the structure and secretory activity of the accessory salivary glands of the marine gastropods, Conus flavidus and C. vexillum (neogastropoda, conacea)
Authors: Schultz Michael C. 
Published: February 2005

AbstractThe structure and secretory activity of the accessory salivary gland in two species of Conus were examined using routine and histochemical techniques of light, scanning and transmission electron microscopy.The composite layers of the accessory salivary gland of Conus are a luminal epithelium, fibromuscular layer, submuscular layer, and a capsule. In C. flavidus and C. vexillum, the luminal epithelium is formed by epitheliocytes and cytoplasmic processes extending from the secretory cells, whose perikarya form the submuscular layer. The processes carry secretory cell products (chiefly Golgi‐derived glycoprotein) across the fibromuscular layer and terminate between epitheliocytes (at the bases of the secretory canaliculi) or beyond the surface of the epithelial cells. Conus vexillum is distinguished from C. flavidus by its high content of lipofuscin. Epitheliocytes are the only microvillated cells in the accessory salivary gland of Conus. In C. flavidus, epitheliocytes extrude secretory granules, various types of cytoplasmic blebs and clear vesicles by apocrine “pinching off”. Clear vesicles are shed from the tips of microvilli. The luminal epithelial cells of C. vexillum similarly egest clear vesicles, but normally undergo additional holocrine secretion to release lipofuscin.The secretions of epitheliocytes appear to be major products of the accessory salivary gland: consideration of secretory activities by both epitheliocytes and secretory cells will therefore be necessary when directly investigating accessory salivary gland function in Conus.
Thoracic morphology of a flightless mexican grasshopper, Barytettix psolus: Comparison with the locust, Schistocerca gregaria
Authors: Arbas Edmund A. 
Published: February 2005

AbstractThe thoracic morphology of a flightless grasshopper, Barytettix psolus, is described and compared to that of locusts, Schistocerca gregaria, to evaluate modifications to skeleton, muscles, and the nervous system which have accompanied secondary loss of flight. Barytettix lacks hindwings, has immobile vestiges of forewings and is devoid of skeletal specializations for wing movement and flight. Its pterothoracic musculature resembles that of Schistocerca except for the absence of those muscles which, in locusts, have the primary function of moving the wings, the dorsal longitudinal, tergosternal, first basalar, pleuroalar, and dorsal accessory muscles. Pterothoracic ganglia of Barytettix resemble those of Schistocerca in their gross features, number, and primary branching pattern of nerves, with differences in detail relating to reduction of the flight muscles. The combination of features exhibited in Barytettix represents an extreme reduction in the specialization for wing movements and flight displayed by most acridids, at a level which exceeds that of many brachypterous and some apterous species. While skeletal fusion and loss of muscles indicate loss of flight, the accompanying thoracic stiffening and increase in overall body density may promote more efficient jumping as a means of locomotion.
Cochlear hair‐cell populations and limits of resolution of hearing in two vespertilionid bats, Nyctalus noctula and Eptesicus serotinus
Authors: Burda Hynek , Úlehlová Libuše 
Published: February 2005

AbstractA comparison of the population of cochlear hair cells with known hearing resolution capabilities in two species of bats (Nyctalus noctula and Eptesicus serotinus of the family Vespertilionidae) has revealed a close correlation between morphological and functional parameters. Data on number and densities of hair cells in the examined bat species are presented. Even though the species are of a comparable body size, N. noctula has a longer basilar membrane, a higher density, and hence also a higher total number of hair cells than E. serotinus. This is in good agreement with hearing resolution capabilities, which are better in N. noctula than in E. serotinus. These findings have implications on differences in feeding ecology and hunting strategies between these species.