scholarly journals A new fossil dolphin Dilophodelphis fordycei provides insight into the evolution of supraorbital crests in Platanistoidea (Mammalia, Cetacea)

2017 ◽  
Vol 4 (5) ◽  
pp. 170022 ◽  
Author(s):  
Alexandra T. Boersma ◽  
Matthew R. McCurry ◽  
Nicholas D. Pyenson
Keyword(s):  
South Asian ◽  
Middle Miocene ◽  
Sound Propagation ◽  
Early Miocene ◽  
New Taxon ◽  
Internal Morphology ◽  
Computed Tomography Scans ◽  
Evolutionary Context ◽  
And Function ◽  
Insight Into

Many odontocete groups have developed enlarged facial crests, although these crests differ in topography, composition and function. The most elaborate crests occur in the South Asian river dolphin ( Platanista gangetica ), in which they rise dorsally as delicate, pneumatized wings anterior of the facial bones. Their position wrapping around the melon suggests their involvement in sound propagation for echolocation. To better understand the origin of crests in this lineage, we examined facial crests among fossil and living Platanistoidea, including a new taxon, Dilophodelphis fordycei , nov. gen. and sp., described herein, from the Early Miocene Astoria Formation of Oregon, USA. We measured the physical extent and thickness of platanistoid crests, categorized their relative position and used computed tomography scans to examine their internal morphology and relative bone density. Integrating these traits in a phylogenetic context, we determined that the onset of crest elaboration or enlargement and the evolution of crest pneumatization among the platanistoids were separate events, with crest enlargement beginning in the Oligocene. However, we find no evidence for pneumatization until possibly the Early Miocene, although certainly by the Middle Miocene. Such an evolutionary context, including data from the fossil record, should inform modelling efforts that seek to understand the diversity of sound generation morphology in Odontoceti.

Gondwanatheria and ?Multituberculata (Mammalia) from the Late Cretaceous of Madagascar

2013 ◽  
Vol 50 (3) ◽  
pp. 324-340 ◽  
Author(s):  
David W. Krause
Keyword(s):  
Late Cretaceous ◽  
New Taxon ◽  
Negative Evidence ◽  
Mammalian Fauna ◽  
Micro Computed Tomography ◽  
Lower Incisor ◽  
Computed Tomography Scans ◽  
Size Variability ◽  
Mammalian Teeth ◽  
Insight Into

In addition to four isolated mammalian teeth from the Late Cretaceous (Maastrichtian) of Madagascar described previously and allocated to Gondwanatheria, Marsupialia, and Mammalia incertae sedis, here I put on record five more specimens. Four of these, a virtually complete lower molariform cheek tooth, two fragmentary cheek teeth, and a fragmentary lower incisor, are referred to the Sudamericidae (Gondwanatheria). The internal structure of the hypsodont cheek teeth, as revealed by micro-computed tomography scans to simulate different stages of wear, is highly variable. Limited knowledge of intra-individual morphological and size variability in the dentition of sudamericids, which are known almost exclusively from isolated teeth, precludes a conclusive assessment of whether some or all of the new specimens belong to Lavanify miolaka, the only previously described sudamericid from Madagascar, or to a new taxon. Conservatively, therefore, pending the recovery of better material, all four specimens are referred to Sudamericidae gen. et sp. indet. The fifth specimen, a molar fragment, is tentatively allocated to the Multituberculata, thereby adding to the controversial specimens that comprise the very sparse and questionable record of this clade on the southern supercontinent Gondwana. The new specimens do not provide any profound insight into the origins of the highly endemic and imbalanced extant mammalian fauna on Madagascar; rather, they provide only more negative evidence. Like those previously described, they do not represent the basal stocks of any of the five mammalian clades that live on the island today and therefore further support the growing consensus that representatives of the extant clades arrived in the Cenozoic.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Computational Approaches to Predict the Non-canonical DNAs

2019 ◽  
Vol 14 (6) ◽  
pp. 470-479 ◽  
Author(s):  
Nazia Parveen ◽  
Amen Shamim ◽  
Seunghee Cho ◽  
Kyeong Kyu Kim
Keyword(s):  
Computational Methods ◽  
Genetic Instability ◽  
Computational Prediction ◽  
Structure And Function ◽  
Sequence Motifs ◽  
Computational Approaches ◽  
Functional Roles ◽  
And Function ◽  
Genetic Events ◽  
Insight Into

Background: Although most nucleotides in the genome form canonical double-stranded B-DNA, many repeated sequences transiently present as non-canonical conformations (non-B DNA) such as triplexes, quadruplexes, Z-DNA, cruciforms, and slipped/hairpins. Those noncanonical DNAs (ncDNAs) are not only associated with many genetic events such as replication, transcription, and recombination, but are also related to the genetic instability that results in the predisposition to disease. Due to the crucial roles of ncDNAs in cellular and genetic functions, various computational methods have been implemented to predict sequence motifs that generate ncDNA. Objective: Here, we review strategies for the identification of ncDNA motifs across the whole genome, which is necessary for further understanding and investigation of the structure and function of ncDNAs. Conclusion: There is a great demand for computational prediction of non-canonical DNAs that play key functional roles in gene expression and genome biology. In this study, we review the currently available computational methods for predicting the non-canonical DNAs in the genome. Current studies not only provide an insight into the computational methods for predicting the secondary structures of DNA but also increase our understanding of the roles of non-canonical DNA in the genome.

scholarly journals Significance of Mast Cell Formed Extracellular Traps in Microbial Defense

2021 ◽  
Author(s):  
Daniel Elieh Ali Komi ◽  
Wolfgang M. Kuebler
Keyword(s):  
State Of The Art ◽  
Extracellular Dna ◽  
Cellular Mechanisms ◽  
Extracellular Traps ◽  
Synthetic Chemicals ◽  
Dna Strands ◽  
Associated Proteins ◽  
Microbial Defense ◽  
And Function ◽  
Insight Into

AbstractMast cells (MCs) are critically involved in microbial defense by releasing antimicrobial peptides (such as cathelicidin LL-37 and defensins) and phagocytosis of microbes. In past years, it has become evident that in addition MCs may eliminate invading pathogens by ejection of web-like structures of DNA strands embedded with proteins known together as extracellular traps (ETs). Upon stimulation of resting MCs with various microorganisms, their products (including superantigens and toxins), or synthetic chemicals, MCs become activated and enter into a multistage process that includes disintegration of the nuclear membrane, release of chromatin into the cytoplasm, adhesion of cytoplasmic granules on the emerging DNA web, and ejection of the complex into the extracellular space. This so-called ETosis is often associated with cell death of the producing MC, and the type of stimulus potentially determines the ratio of surviving vs. killed MCs. Comparison of different microorganisms with specific elimination characteristics such as S pyogenes (eliminated by MCs only through extracellular mechanisms), S aureus (removed by phagocytosis), fungi, and parasites has revealed important aspects of MC extracellular trap (MCET) biology. Molecular studies identified that the formation of MCET depends on NADPH oxidase-generated reactive oxygen species (ROS). In this review, we summarize the present state-of-the-art on the biological relevance of MCETosis, and its underlying molecular and cellular mechanisms. We also provide an overview over the techniques used to study the structure and function of MCETs, including electron microscopy and fluorescence microscopy using specific monoclonal antibodies (mAbs) to detect MCET-associated proteins such as tryptase and histones, and cell-impermeant DNA dyes for labeling of extracellular DNA. Comparing the type and biofunction of further MCET decorating proteins with ETs produced by other immune cells may help provide a better insight into MCET biology in the pathogenesis of autoimmune and inflammatory disorders as well as microbial defense.

scholarly journals Rhinocerotidae from the early Miocene of the Negev (Israel) and implications for the dispersal of early Neogene rhinoceroses

2021 ◽  
pp. 1-12
Author(s):  
Luca Pandolfi ◽  
Ran Calvo ◽  
Ari Grossman ◽  
Rivka Rabinovich
Keyword(s):  
Southeast Asia ◽  
South Asian ◽  
North Africa ◽  
Range Expansion ◽  
New Records ◽  
Ct Scanning ◽  
Early Miocene ◽  
Early Neogene ◽  
Postcranial Remains

Abstract A revision of the rhinocerotid material from the Negev (Israel), dating back to the early Miocene (MN3 in the European Mammal Biochronology), highlights the presence of Brachypotherium and a taxon close to Gaindatherium in the Levantine corridor. A juvenile mandible, investigated using CT scanning, displays morphologically distinct characters consistent with Brachypotherium cf. B. snowi rather than with other Eurasian representatives of this genus. Some postcranial remains from the Negev, such as a humerus, display features that distinguish it among Miocene taxa. We attribute these postcrania to cf. Gaindatherium sp., a taxon never recorded outside the Siwaliks until now. This taxon dispersed into the Levantine region during the late early Miocene, following a pattern similar to other South Asian taxa. Brachypotherium cf. B. snowi probably occurred in the Levantine region and then in North Africa during the early Miocene because its remains are known from slightly younger localities such as Moghara (Egypt) and Jebel Zelten (Libya). The occurrence cf. Gaindatherium sp. represents a previously unrecorded range expansion out of Southeast Asia. These new records demonstrate the paleogeographic importance of the Levantine region showcasing the complex role of the Levantine corridor in intercontinental dispersals between Asia and Europe as well as Eurasia and Africa.

A new species of Sclerocephalus with a fully ossified endocranium gives insight into braincase evolution in temnospondyls

2021 ◽  
pp. 1-13
Author(s):  
Rainer R. Schoch ◽  
Gabriela Sobral
Keyword(s):  
New Species ◽  
Character Evolution ◽  
Late Paleozoic ◽  
New Taxon ◽  
Early Permian ◽  
Top Predator ◽  
Central European ◽  
Wide Range ◽  
A New Species ◽  
Insight Into

Abstract The late Paleozoic temnospondyl Sclerocephalus formed an aquatic top predator in various central European lakes of the late Carboniferous and early Permian. Despite hundreds of specimens spanning a wide range of sizes, knowledge of the endocranium (braincase and palatoquadrate) remained very insufficient in Sclerocephalus and other stereospondylomorphs because even large skulls had unossified endocrania. A new specimen from a stratigraphically ancient deposit at St. Wendel in southwestern Germany is recognized as representing a new taxon, S. concordiae new species, and reveals a completely ossified endocranium. The sphenethmoid was completely ossified from the basisphenoid to the anterior ethmoid region, co-ossified with the parasphenoid, and the basipterygoid joint was fully established. The pterygoid bears a slender, S-shaped epipterygoid, which formed a robust pillar lateral to the braincase. The massive stapes was firmly sutured to the parasphenoid. In the temnospondyl endocranium, character evolution involved various changes in the epipterygoid region, which evolved distinct morphologies in each of the major clades. UUID: http://zoobank.org/5e6d2078-eacf-4467-84cf-a12efcae7c0b

Regulation of hair follicle development by the TNF signal ectodysplasin and its receptor Edar

Development ◽  
2002 ◽  
Vol 129 (10) ◽  
pp. 2541-2553 ◽  
Author(s):  
Johanna Laurikkala ◽  
Johanna Pispa ◽  
Han-Sung Jung ◽  
Pekka Nieminen ◽  
Marja Mikkola ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Hair Follicles ◽  
Wild Type ◽  
Mutant Mouse Embryos ◽  
Anhidrotic Ectodermal Dysplasia ◽  
Embryonic Morphogenesis ◽  
Hair Follicle Development ◽  
And Function ◽  
Insight Into

X-linked and autosomal forms of anhidrotic ectodermal dysplasia syndromes (HED) are characterized by deficient development of several ectodermal organs, including hair, teeth and exocrine glands. The recent cloning of the genes that underlie these syndromes, ectodysplasin (ED1) and the ectodysplasin A receptor (EDAR), and their identification as a novel TNF ligand-receptor pair suggested a role for TNF signaling in embryonic morphogenesis. In the mouse, the genes of the spontaneous mutations Tabby (Ta) and downless (dl) were identified as homologs of ED1 and EDAR, respectively. To gain insight into the function of this signaling pathway in development of skin and hair follicles, we analyzed the expression and regulation of Eda and Edar in wild type as well as Tabby and Lef1 mutant mouse embryos. We show that Eda and Edar expression is confined to the ectoderm and occurs in a pattern that suggests a role of ectodysplasin/Edar signaling in the interactions between the ectodermal compartments and the formation and function of hair placodes. By using skin explant cultures, we further show that this signaling pathway is intimately associated with interactions between the epithelial and mesenchymal tissues. We also find that Ta mutants lack completely the placodes of the first developing tylotrich hairs, and that they do not show patterned expression of placodal genes, including Bmp4, Lef1, Shh, Ptch and Edar, and the genes for β-catenin and activin A. Finally, we identified activin as a mesenchymal signal that stimulates Edar expression and WNT as a signal that induces Eda expression, suggesting a hierarchy of distinct signaling pathways in the development of skin and hair follicles. In conclusion, we suggest that Eda and Edar are associated with the onset of ectodermal patterning and that ectodysplasin/edar signaling also regulates the morphogenesis of hair follicles.

Foraminifera Biostratigraphy of Two Wells in Niger Delta

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Dairo VA
Keyword(s):  
Niger Delta ◽  
Middle Miocene ◽  
Early Miocene ◽  
Orbulina Universa ◽  
Exploratory Wells ◽  
Stratigraphic Range

Biostratigraphic studies of foraminifera were carried out on two exploratory wells drilled in the Eastern Niger Delta to establish the age, biozonation and paleoenvironment of the foraminifera present in the strata penetrated by the wells. A total of 80 ditch cutting samples retrieved at 60ft intervals from AX-1 and AX-2 Wells at the depth of 3,600ft to 6,000ft and 4,200ft to 6500ft. respectively were subjected to micropaleontological analysis which involves picking and identification of the foraminifera present. The resulting data were loaded into the Stratabug software and interpreted. The foraminifera recovered and identified from the two wells are made up of both benthic and planktic species. The marker species, whose stratigraphic range are well established were used to describe the biozonation and these includes Heterostegina sp, Catapsydrax stainforthi, Chiloguembelina victoriana, Orbulina universa/suturalis, Praeorbulina sicana,Buliminella subfusiformis, Nonion centrosulcatum, Catapsydrax dissimilis, Globigerinoides bisphericus and Globigerinoides sicanus. Four biozones of foraminifera made up of N8, N7-N8, N6-N7 and N5-N6 were recognised based on the zonation scheme of Grandstein; with their stratigraphic age ranging from early Miocene to middle Miocene. Furthermore, the environment of deposition prevailing in the Formations penetrated by the two wells are predominantly middle neritic with similarity in their ages as observed from the correlation of the biozones from the two wells

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