bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphogenesis of extraembryonic membranes and placentation in Mabuya mabouya (Squamata, Scincidae)
Authors: Jerez Adriana , Ramírez‐Pinilla Martha Patricia 
Published: September 2003

AbstractTopological and histological analyses of Mabuya mabouya embryos at different developmental stages showed an extraembryonic membrane sequence as follows: a bilaminar omphalopleure and progressive mesodermal expansion around the whole yolk sac at gastrula stages; mesodermal split and formation of an exocoelom in the entire embryonic chamber at neurula stages; beginning of the expansion of the allantois into the exocoelom to form a chorioallantoic membrane at pharyngula stages; complete extension of the allantois into the exocoelom between limb‐bud to preparturition stages. Thus, a placental sequence could be enumerated: bilaminar yolk sac placenta; chorioplacenta; allantoplacenta. All placentas are highly specialized for nutrient absorption from early developmental stages. The bistratified extraembryonic ectoderm possesses an external layer with cuboidal cells and a microvillar surface around the whole yolk sac, which absorbs uterine secretions during development of the bilaminar yolk sac placenta and chorioplacenta. During gastrulation, with mesodermal expansion a dorsal absorptive plaque forms above the embryo and several smaller absorptive plaques develop antimesometrially. Both structures are similar histologically and are active in histotrophic transfer from gastrula stages until the end of development. The dorsal absorptive plaque will constitute the placentome and paraplacentome during allantoplacental development. At late gastrula–early neurula stages some absorptive plaques form chorionic concavities or chorionic bags that are penetrated by a long uterine fold and seem to have a specialized histotrophic and/or metabolic role. The extraembryonic mesoderm does not ingress into the yolk sac and neither an isolated yolk mass nor a yolk cleft are formed. This derived pattern of development may be related to the drastic reduction of the egg size and obligatory placentotrophy from early developmental stages. Our results show new specialized placentotrophic structures and a novel arrangement of extraembryonic membrane morphogenesis for Squamata. J. Morphol. 258:158–178, 2003. © 2003 Wiley‐Liss, Inc.
Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona)
Authors: Scheltinga David M. , Wilkinson Mark , Jamieson Barrie G.M. , Oommen Oommen V. 
Published: September 2003

AbstractThe spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta‐axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapomorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, and 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Anura. J. Morphol. 258:179–192, 2003. © 2003 Wiley‐Liss, Inc.
Diversification of brain and sense organ morphology in antarctic dragonfishes (Perciformes: Notothenioidei: Bathydraconidae)
Authors: Eastman Joseph T. , Lannoo Michael J. 
Published: September 2003

AbstractIn the subzero shelf waters of Antarctica, fishes of the perciform suborder Notothenioidei dominate the fish fauna and constitute an adaptive radiation and a species flock. The 16 species of dragonfishes of the family Bathydraconidae live from surface waters to nearly 3,000 m and have the greatest overall depth range among notothenioid families. We examined the anatomy and histology of the brain, retina, and cephalic lateral line system of nine bathydraconid species representing 8 of the 11 known genera. We evaluate these data against a cladogram identifying three clades in the family. We provide a detailed drawing of the brain and cranial nerves of Gymnodraco acuticeps and Akarotaxis nudiceps. Bathydraconid brain morphology falls into two categories. Brains of most species are similar to those of generalized perciforms and some basal notothenioids (Class I). However, brains of deep‐living bathydraconids (members of the tribe Bathydraconini minus Prionodraco) have a reduced telencephalon and tectum that renders the neural axis visible — the stalked brain morphology (Class II). All bathydraconids have duplex (rod and cone) retinae but there is considerable interspecific variation in the ratio of cones:rods and in the number of cells in the internal nuclear layer. Retinal histology reflects habitat depth but is not tightly coupled to phylogeny. Although the deep‐living species of Bathydraconini have rod‐dominated retinae, the retinae of some sister species are photopic. An expanded cephalic lateral line system is also characteristic of all members of the Bathydraconini as exemplified by Akarotaxis. This morphology includes large lateral line pores, wide membranous canals, hypertrophied canal neuromasts, and large anterodorsal lateral line nerves, eminentia granulares, and crista cerebellares. The saccular otoliths are also enlarged in members of this tribe. Neural diversification among bathydraconids on the Antarctic shelf has not involved the evolution of sensory specialists. Brain and sense organ morphologies do not approach the specialized condition seen in primary deep‐sea fishes or even that of some secondary deep‐sea fishes including sympatric non‐notothenioids such as liparids (snailfishes) and muraenolepidids (eel cods). The brains and sense organs of bathydraconids, including the deep‐living species, reflect their heritage as perciform shorefishes. J. Morphol. 258:130–150, 2003. © 2003 Wiley‐Liss, Inc.
Fetal development of the segment‐specific papillary body in the equine hoof
Authors: Bragulla Hermann 
Published: September 2003

AbstractFetal development of the unique papillary body and its localized peculiarities in the equine hoof are described based on the study of 51 fetuses, nine newborn foals, and five adult horses. The shape and dimensions of the dermal papillae and lamellae have a formative influence on the structure and physical quality of the corneous hoof capsule with its horn tubules and lamellae. The size and arrangement of these horn structures determine the mechanical quality of hoof horn. Proper horn quality is a prerequisite for the various functions of the hoof capsule, such as protecting the living dermis supporting the hoof capsule, shock absorption, and formation of the suspensory apparatus of the distal phalanx. Development of the segment‐specific papillary body is initiated by the increasing mitotic activity of the epidermal cells invaginating the dermal surface, thus forming dermal microridges. These microridges are transformed into single dermal papillae, which are arranged in rows, or enlarged to become primary and secondary dermal lamellae. The formation of a segment‐specific papillary body enables the increasing keratinization ratio in the hoof epidermis and the formation of the characteristic tubular and lamellar horn responsible for the special mechanical properties of hoof horn. J. Morphol. 258:207‐224, 2003. © 2003 Wiley‐Liss, Inc.
The term “lateral recess” and craniofacial pneumatization in old world monkeys (Mammalia, Primates, Cercopithecoidea)
Authors: Rae Todd C. , Koppe Thomas 
Published: September 2003

AbstractThe primate superfamily Cercopithecoidea (or Old World monkeys) is characterized by a widespread lack of the maxillary sinus, a paranasal pneumatic space found in most other eutherian mammals. Previous discussions of the distribution of pneumatization in the group, however, have been ambiguous and contradictory, and have been further complicated by discussion of a poorly defined structure named the “lateral recess,” linked implicitly to the maxillary sinus. Computed tomography (CT) was applied to dry crania of all cercopithecoid genera to evaluate the morphological relevance of the term “lateral recess.” Results suggest that the “lateral recess” is a structural consequence of changes in skull form unrelated to pneumatization. Thus, the term should be abandoned. All Old World monkeys (except the genus Macaca) are found to lack the maxillary sinus, but a previously undescribed bulla, only separated from the nasal cavity anteriorly, was discovered in the Chinese golden monkey Rhinopithecus. If this bulla is related to the paranasal sinuses, it suggests that the initial change in cercopithecoid cranial evolution was a suppression of pneumatic development, which may have been subsequently reversed twice in the history of the group, in Macaca and Rhinopithecus. J. Morphol. 258:193–199, 2003. © 2003 Wiley‐Liss, Inc.
Alimentary tract of kowalevskiidae (appendicularia, tunicata) and evolutionary implications
Authors: Brena Carlo , Cima Francesca , Burighel Paolo 
Published: September 2003

AbstractThe alimentary tract of Kowalevskia tenuis and K. oceanica, the only species of the appendicularian family Kowalevskiidae, was studied both at the light and electron microscope levels and compared with species belonging to the other two families of the class. Kowalevskids show interesting specializations: 1) the pharynx opens on both sides through two opposing spiracles, modified into long ciliated fissures, and possesses an original filtering system of ciliated combs arranged in two pairs of opposing longitudinal rows; 2) the endostyle is absent, its place being taken by a ciliated groove without any glandular cell; 3) posterior to the esophagus, the globular stomach and rectum form a digestive nucleus comprising a few, large cells including two well‐developed, specialized valves, cardiac and pyloric; 4) special apical junctions bearing characteristics of both gap and adherens junctions are diffuse along the gut epithelium; 5) the heart is absent. Our data suggest that Kowalevskiidae underwent a high degree of specialization for food filtering and are more closely related to Fritillariidae, with which they share several characters, rather than Oikopleuridae, the latter probably representing the most primitive family of appendicularians. J. Morphol. 258:225–238, 2003. ©2003 Wiley‐Liss, Inc.
Patterns of ossification in the manus of the harbor porpoise (Phocoena phocoena): Hyperphalangy and delta‐shaped bones
Authors: Dawson Susan D. 
Published: September 2003

AbstractWith the transition from terrestrial to aquatic habitats, cetacean forelimbs have undergone significant modifications in bone morphology and soft tissue distribution. Some, but not all, of these modifications are also demonstrated in other lineages of extant and extinct secondarily aquatic tetrapods. This study examines the ontogenetic pattern of ossification of the manus of the harbor porpoise (Phocoena phocoena), using plain film radiography. Two modifications examined are hyperphalangy (number of phalanges per digit increased beyond the typical mammalian number) and the morphology of delta‐shaped bones. Hyperphalangy in Phocoena phocoena is apparent in digits 2 and 3. Phalangeal counts in all digits are variable (sometimes between the right and left flippers of the same individual) and are not necessarily correlated with age. Phalangeal ossification and epiphyseal fusion proceeds along the proximo–distal axis within each digit. In addition, digits 2 and 3 are at a more advanced stage of ossification than more abaxial digits. Delta‐shaped bones appear to be a normal stage in the ossification of phalanges in all digits except the third, and may persist in the adult in certain digits. In humans, this morphology is a developmental anomaly usually associated with other malformations, such as polydactyly or syndactyly. Delta‐shaped bones in the cetacean manus display a consistent orientation and the process by which they are formed may be similar to that in extinct marine reptiles. J. Morphol. 258:200–206, 2003. © 2003 Wiley‐Liss, Inc.
Scale microornamentation of uropeltid snakes
Authors: Gower David J. 
Published: September 2003

AbstractMicroornamentation was examined on the exposed oberhautchen surface of dorsal, lateral, and ventral scales from the midbody region of 20 species of the fossorial snake family Uropeltidae and seven species of fossorial scolecophidian and anilioid outgroups. No substantial variation was observed in microornamentation from the different areas around the midbody circumference within species. All oberhautchen cells were flat and exhibited no major surface features other than occasional posterior margin denticulations, small pores/pits, and narrow, low ridges. This is largely consistent with the hypothesis that friction reduction and dirt shedding are the main selective pressures on microornamentation, given that reducing shine is not of key importance in fossorial animals. Variations among taxa were observed in the shape and size of oberhautchen cells, in the presence of pores/pits, in the presence and size of denticulations on posterior cell margins, and in the level or imbricate nature of cell borders. Six microornamentation characters were formulated, scored, and plotted onto a selected phylogeny. Character evolution and phylogenetic signal were explored, accepting the incomplete understanding of intraspecific variation and of uropeltid interrelationships. There is evidence that all but one of these characters evolved homoplastically, probably by multiple independent origin. There is no clear evidence for character state reversal, but greater phylogenetic resolution is required to test this further. Phylogenetic signal appears to exist in some instances, including possible microornamentation synapomorphies for Uropeltidae and Melanophidium. These derived character states are found elsewhere within Squamata. A microornamentation of narrow, finely, and regularly spaced ridges is associated with scale iridescence. These ridges, and possibly pores/pits, are also associated with scales that are less wettable, and that therefore might be expected to be better at shedding dirt in moist conditions. Testable hypotheses are presented that might explain minor variations in the form of ridges and pits among uropeltids. J. Morphol. 258:249–268, 2003. © 2003 Wiley‐Liss, Inc.
Morphology of the midgut trunk in the penaeid shrimp, Sicyonia ingentis, highlighting novel nuclear pore particles and fixed hemocytes
Authors: Martin Gary G. , Chiu Alice 
Published: September 2003

AbstractThe morphology of the midgut trunk (MGT) in the penaeid shrimp Sicyonia ingentis was examined by light and scanning and transmission electron microscopy. Although the function of the MGT is poorly understood, it is not involved with the digestion and absorption of nutrients, and it appears to be the surface of a shrimp least protected from penetration by potential pathogens. As described for other decapod crustaceans, the MGT in shrimp is composed of a simple columnar epithelium separated from a layer of connective tissue by a thick basal lamina. Beneath the basal lamina is a previously unreported layer of hemocytes, exclusively of the granulocyte variety, embedded in a matrix continuous with the basal lamina and extending into the connective tissue. This layer was observed in four other species of penaeid shrimp. Granulocytes in circulation can phagocytose and encapsulate foreign material and the granules contain antibacterial molecules, lysosomal enzymes, and prophenoloxidase. We suggest that the granulocytes associated with the basal lamina have matured at this site and are well positioned to fight potential pathogens that have penetrated the epithelial layer of the MGT. A second observation is the presence of clusters of cylinders bound to the nuclear pores of the epithelial cells. The possibility that these clusters are viruses, organelles, or abnormal organelles induced by disease or toxic materials is discussed. These unique particles were observed in S. ingentis but none of the other penaeid shrimp we examined. J. Morphol. 258:239–248, 2003. © 2003 Wiley‐Liss, Inc.
Role of manganese(II), micelles, and inorganic salts on the kinetics of the redox reaction of L‐sorbose and chromium(VI)
Authors: Kabir‐Ud‐Din  , Morshed Abu Mohammad Azmal , Khan Zaheer 
Published: September 2003

AbstractThe kinetics of the reduction of chromium(VI) to chromium(III) by L‐sorbose in HClO4 was studied between 30 and 80°C at various concentrations of reactants and acidities in both aqueous and micellar sodium dodecyl sulfate (SDS)/TritonX‐100(TX‐100) solutions. Under pseudo‐first‐order conditions the reaction rate is fractional‐order in [L‐sorbose] and [H+], and first‐order in [CrVI] both in the absence and in the presence of surfactant micelles. The reaction is accelerated by addition of manganese(II) and is routed through the same mechanism as shown by the kinetic studies in the absence and presence of surfactants. The rate enhancement in presence of SDS/TX‐100 micelles indicates that essentially all the reactive species are bound to micelles under the experimental conditions. The observed catalyses are explained with the modified Menger and Portnoy model. Inorganic salts (NaBr, LiBr, NH4Br) inhibit the reaction in presence of SDS micelles, which confirms exclusion of the reactive species of chromium(VI) from the reaction site. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 543–554, 2003
Kinetics and mechanisms of transalkylation and disproportionation of meta‐diethylbenzene by triflic acid catalyst
Authors: Al‐Zahrani S. M. , Al‐Kinany M. C. , Al‐Humaizi K. I. , Al‐Khowaiter S. H. 
Published: September 2003

AbstractThe kinetics of transalkylation and isomerization of meta‐diethylbenzene in the presence of benzene using triflic acid as a catalyst has been investigated. High catalytic activity of the triflic acid catalyst was observed in homogeneous liquid‐phase reactions. On the basis of the product distribution obtained, transalkylation, disproportionation, and isomerization reactions have been considered and the main product of the reaction was ethylbenzene. These reactions are conducted in a closed liquid batch reactor with continuous stirring under dry nitrogen and atmospheric pressure over the temperature range of 288–308 K. The main transalkylation, disproportionation, and isomerization reactions occurred simultaneously and were considered as elementary reactions. The apparent activation energy of the transalkylation reaction was found to be 35.5 kJ/mol, while that of disproportionation reaction was 42.3 kJ/mol. The reproducibility of the experimental product distribution occurred with an average relative error of ±2%. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 555–563, 2003
Kinetics of amino acid racemization (epimerization) in the dentine of fossil and modern bear teeth
Authors: Canoira Laureano , García‐Martínez Maria‐Jesús , Llamas Juan F. , Ortíz José E. , Torres Trinidad De 
Published: September 2003

AbstractThe present study examines the question of whether heating experiments on modern bear teeth dentine model the pattern of D/L racemization in fossil teeth. Using samples of modern bear teeth dentine heated at 65°C, 85°C (up to 53 days), and 105°C (up to 71 days), and three independently dated fossil bear teeth, we have compared the modes of racemization induced by temperature in the modern samples and by time on the fossil samples. We have studied seven amino acids (aspartic and glutamic acids, alanine, valine, leucine, isoleucine, and phenylalanine) that follow a reversible first‐order kinetic model of racemization (epimerization) either at low or high temperature. We have estimated the Arrhenius parameters, the activation energy Ea and the frequency factor A, first based on the heating experiments, and later including the fossil data. Valine shows no appreciable differences in Ea and A in both estimations, and could then be used with confidence in dating studies. In a lesser extension this also applies to alanine, phenylalanine, leucine, and glutamic acid. Aspartic acid shows a great difference between the temperature‐induced and the time‐induced racemization kinetic models, and it should be used with special care in dating studies, since diagenetic racemization in aspartic acid is extremely sensitive to the thermal history of the site. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 576–591, 2003
Experimental and kinetic modeling study of the effect of NO and SO2 on the oxidation of COH2 mixtures
Authors: Dagaut Philippe , Lecomte Franck , Mieritz Jacob , Glarborg Peter 
Published: September 2003

AbstractThe effect of NO and SO2 on the oxidation of a COH2 mixture was studied in a jet‐stirred reactor at atmospheric pressure and for various equivalence ratios (0.1, 1, and 2) and initial concentrations of NO and SO2 (0–5000 ppm). The experiments were performed at fixed residence time and variable temperature ranging from 800 to 1400 K. Additional experiments were conducted in a laminar flow reactor on the effect of SO2 on COH2 oxidation in the same temperature range for stoichiometric and reducing conditions. It was demonstrated that in fuel‐lean conditions, the addition of NO increases the oxidation of the COH2 mixture below 1000 K and has no significant effect at higher temperatures, whereas the addition of SO2 has a small inhibiting effect. Under stoichiometric and fuel‐rich conditions, both NO and SO2 inhibit the oxidation of the COH2 mixture. The results show that a COH2 mixture has a limited NO reduction potential in the investigated temperature range and rule out a significant conversion of HNO to NH through reactions like HNO + CO ⇔︁ NH + CO2 or HNO + H2 ⇔︁ NH + H2O. The chain terminating effect of SO2 under stoichiometric and reducing conditions was found to be much more pronounced than previously reported under flow reactor conditions and the present results support a high rate constant for the H + SO2 + M ⇔︁ HOSO + M reaction. The reactor experiments were used to validate a comprehensive kinetic reaction mechanism also used to simulate the reduction of NO by natural gas blends and pure C1 to C4 hydrocarbons. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 564–575, 2003