scholarly journals Shell Anomalies in the European Aquatic Stem Turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Diversity ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 518
Author(s):  
Andrea Guerrero ◽  
Adán Pérez-García
Keyword(s):  
Sexual Dimorphism ◽  
Broad Spectrum ◽  
Morphological Variation ◽  
Lower Cretaceous ◽  
Individual Variability ◽  
Ontogenetic Development ◽  
Negative Consequences ◽  
Detailed Characterization ◽  
Good Preservation

The uppermost Jurassic to lowermost Cretaceous stem turtle Pleurosternon bullockii is the pleurosternid (Testudinata, Paracryptodira) known by the largest number of specimens worldwide, composing the largest European collection of Lower Cretaceous complete and partial shells for a turtle taxon. The availability of numerous specimens as well as their generally good preservation allowed for recent detailed characterization of the shell of this species, including states that are variable at the intraspecific level (individual variability, sexual dimorphism, and ontogenetic development). However, extreme cases of morphological variation corresponding to anomalies have not been addressed in detail, neither for P. bullockii nor for any other member of Paracryptodira. In this context, the study of several shell anomalies in P. bullockii is carried out here. Fourteen specimens showing anomalies are recognized and examined here to determine the frequency and distribution of these shell anatomical deviations. All these anomalies are described and figured. The morphogenetic cause of each of them is discussed. As a consequence, a relatively broad spectrum of anomalies is reported for P. bullockii. None of the anomalies seem to present negative consequences for vital activities of the specimens since none compromised the main functions of the shell.

Sur la présence d'une nouvelle espèce d'Isoetites dans la flore du Crétacé inférieur de la région de Tataouine (Sud tunisien) : implications paléoclimatiques et phylogénétiques

1999 ◽  
Vol 77 (2) ◽  
pp. 189-196 ◽  
Author(s):  
Georges Barale
Keyword(s):  
New Species ◽  
Morphological Variation ◽  
Lower Cretaceous ◽  
Growth And Development ◽  
Fossil Plant ◽  
Deltaic Plain ◽  
Good Preservation ◽  
First Time ◽  
A New Species ◽  
South Tunisia

Fossil plant compressions belonging to Isoetales have been discovered, for the first time, in clay from the Lower Cretaceous of Merbah el Asfer, Tataouine area (south Tunisia). The study of leafy corms and sporophylls has permitted us to attribute the fossils to the genus Isoetites Münster. The comparison between the known Mesozoic material leads to the description of a new species : I. daharensis nov.sp. Its affinities with Isoetes and with Triassic species show that the Isoetales were differentiated before the beginning of the Mesozoic era, and since then this lineage has shown little morphological variation. The good preservation of fossils is evidence of short transportation in a deltaic plain with sufficient moisture to permit the growth and development of these plants.Key words: Isoetales, Isoetites, Lower Cretaceous, Tunisia, phylogeny, palaeoecology.

RHYNCHOLITES AND THE PROBLEM OF NARROW AND BROAD CONCEPTION OF TAXONS

2018 ◽  
pp. 12-17 ◽  
Author(s):  
I. R. Khuzina ◽  
V. N. Komarov
Keyword(s):  
Sexual Dimorphism ◽  
Morphological Characteristics ◽  
Mass Scale ◽  
Individual Variability ◽  
Point Of View ◽  
The Other ◽  
New Taxon ◽  
Artificial System ◽  
Broad Understanding

The paper considers a point of view, based on the conception of the broad understanding of taxons. According to this point of view, rhyncholites of the subgenus Dentatobeccus and Microbeccus are accepted to be synonymous with the genus Rhynchoteuthis, and subgenus Romanovichella is considered to be synonymous with the genus Palaeoteuthis. The criteria, exercising influence on the different approaches to the classification of rhyncholites, have been analyzed (such as age and individual variability, sexual dimorphism, pathological and teratological features, degree of disintegration of material), underestimation of which can lead to inaccuracy. Divestment of the subgenuses Dentatobeccus, Microbeccus and Romanovichella, possessing very bright morphological characteristics, to have an independent status and denomination to their synonyms, has been noted to be unjustified. An artificial system (any suggested variant) with all its minuses is a single probable system for rhyncholites. The main criteria, minimizing its negative sides and proving the separation of the new taxon, is an available mass-scale material. The narrow understanding of the genus, used in sensible limits, has been underlined to simplify the problem of the passing the view about the genus to the other investigators and recognition of rhyncholites for the practical tasks.

Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

2020 ◽  
Author(s):  
Wallace Derricotte ◽  
Huiet Joseph
Keyword(s):  
Chemical Potential ◽  
Reaction Force ◽  
Intramolecular Proton Transfer ◽  
Intermediate Energy ◽  
Force Analysis ◽  
Activation Energy Barrier ◽  
Detailed Characterization ◽  
Proton Transfers ◽  
Reaction Force Constant

The mechanism of isomerization of hydroxyacetone to 2-hydroxypropanal is studied within the framework of reaction force analysis at the M06-2X/6-311++G(d,p) level of theory. Three unique pathways are considered: (i) a step-wise mechanism that proceeds through formation of the Z-isomer of their shared enediol intermediate, (ii) a step-wise mechanism that forms the E-isomer of the enediol, and (iii) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol<sup>-1</sup>. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism.

DETAILED CHARACTERIZATION OF EUROPA'S RIDGE MORPHOLOGY

2016 ◽  
Author(s):  
Janelle A.F. Heitmeier ◽  
◽  
Emily S. Martin ◽  
Jordan M. Bretzfelder ◽  
D. Alex Patthoff ◽  
...  
Keyword(s):  
Detailed Characterization

The Problem of Divine Hiddenness

2018 ◽  
Author(s):  
Michael C. Rea
Keyword(s):  
Problem Of Evil ◽  
Philosophical Discussion ◽  
Detailed Characterization ◽  
The Past ◽  
Divine Hiddenness ◽  
The Problem Of Evil ◽  
The Relationship

This chapter provides a detailed characterization of the various meanings of the term “divine hiddenness,” carefully and rigorously articulates the version of the problem of divine hiddenness that has dominated contemporary philosophical discussion for the past twenty-five years, and then explains the relationship between that problem and the problem of evil.

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

Impulsivity and Drug Addiction: A Neurobiological Perspective

2012 ◽  
Author(s):  
Trevor Robbins
Keyword(s):  
Drug Addiction ◽  
Conceptual Analysis ◽  
Animal Studies ◽  
Reaction Time Task ◽  
Compulsive Behavior ◽  
Self Administration ◽  
Detailed Characterization ◽  
Cocaine Seeking ◽  
Serial Reaction

A conceptual analysis of the impulsivity construct in behavioral and neurobiological terms is followed by an analysis of its causal role in certain forms of drug addiction in both human and animal studies. The main focus of this chapter is on a rat model of impulsivity based on premature responding in the five-choice serial reaction time task and a more detailed characterization of this phenotype in neurobehavioral, neurochemical, and genetic terms. Evidence is surveyed that high impulsivity on this task is associated with the escalation subsequently of cocaine self-administration behavior and also with a tendency toward compulsive cocaine seeking. Novelty reactivity, by contrast, is associated with the enhanced acquisition of self-administration, but not with the escalation of intravenous self-administration of cocaine or the development of compulsive behavior associated with cocaine seeking. These results indicate that the vulnerability to stimulant addiction may depend on different factors, as expressed through distinct presumed endophenotypes. These observations help us further to dissociate various aspects of the impulsivity construct in neural as well as behavioral terms.

scholarly journals New Trimethoprim-Like Molecules: Bacteriological Evaluation and Insights into Their Action

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 709
Author(s):  
Marta Jorba ◽  
Marina Pedrola ◽  
Ouldouz Ghashghaei ◽  
Rocío Herráez ◽  
Lluis Campos-Vicens ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Efflux Pump ◽  
Synergistic Effects ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Detailed Characterization ◽  
Low Concentrations ◽  
Pump Activity ◽  
Bacteriological Evaluation ◽  
Kinetics Of

This work reports a detailed characterization of the antimicrobial profile of two trimethoprim-like molecules (compounds 1a and 1b) identified in previous studies. Both molecules displayed remarkable antimicrobial activity, particularly when combined with sulfamethoxazole. In disk diffusion assays on Petri dishes, compounds 1a and 1b showed synergistic effects with colistin. Specifically, in combinations with low concentrations of colistin, very large increases in the activities of compounds 1a and 1b were determined, as demonstrated by alterations in the kinetics of bacterial growth despite only slight changes in the fractional inhibitory concentration index. The effect of colistin may be to increase the rate of antibiotic entry while reducing efflux pump activity. Compounds 1a and 1b were susceptible to extrusion by efflux pumps, whereas the inhibitor phenylalanine arginyl β-naphthylamide (PAβN) exerted effects similar to those of colistin. The interactions between the target enzyme (dihydrofolate reductase), the coenzyme nicotinamide adenine dinucleotide phosphate (NADPH), and the studied molecules were explored using enzymology tools and computational chemistry. A model based on docking results is reported.

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