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  • 1
    ISSN: 1432-1424
    Keywords: Cerebellar granule neuron ; Heloderma horridum ; Helothermine ; Potassium current ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Helothermine, a recently isolated toxin from the venom of the Mexican beaded lizard Heloderma horridum horridum was tested on K+ currents of newborn rat cerebellar granule cells. In whole-cell voltageclamp experiments, cerebellar granule neurons exhibited at least two different K+ current components: a first transient component which is similar to an I A-type current, is characterized by fast activating and inactivating kinetics and blocked by 4-aminopyridine; a second component which is characterized by noninactivating kinetics, is blocked by tetraetylammonium ions and resembles the classical delayed-rectifier current. When added to the standard external solution at concentrations ranging between 0.1 and 2 μm helothermine reduced the pharmacologically isolated I A-type current component in a voltage- and dose-dependent way, with a half-maximal inhibitory concentration (IC50) of 0.52 μm. A comparison between control and nelothermine-modified peak transient currents shows a slowdown of activation and inactivation kinetics. The delayed-rectifier component inhibition was concentration dependent (IC50 = 0.86 μm) but not voltage dependent. No frequency-or use-dependent block was observed on both K+ current types. Perfusing the cells with control solution resulted in quite a complete current recovery. We conclude that helothermine acts with different affinities on two types of K+ current present in central nervous system neurons.
    Type of Medium: Electronic Resource
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  • 2
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    In:  Scripta Geologica vol. 122, pp. 123-151
    Publication Date: 2024-01-12
    Description: Abundant fossils of the bear Indarctos atticus (Weithofer, 1888) from the Lower Turolian (MN11) site of Crevillente 2 (Alicante, Spain) and some new material from the Middle Turolian (MN12) of Concud and Valdecebro 5 (Teruel, Spain) are described. On the other hand some dental remains from Crevillente 2 are identified as Indarctos sp. cf. I. vireti Villalta & Crusafont, 1943 on the basis of their small size. The status of different Indarctos species are discussed.
    Keywords: Mammalia ; Ursidae ; Miocene ; Spain
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
    Publication Date: 2024-01-12
    Description: The Cerro de los Batallones (Los Batallones Butte) is located in the central-northern area of the Madrid Basin, central Spain. Nine vertebrates localities containing a large variety of mammals of Upper Vallesian Age (Late Miocene) have been found associated with the sediments forming the butte. From bottom to top, these sediments consist of magnesian lutite beds (Unit I), paleosols formed of sepiolite and opal (Unit II), and siliclastic, marlstone and carbonate beds (Unit III). The set of ERT profiles developed in Los Batallones Butte have demonstrate that electrical imaging techniques are an estimable tool for the characterization and prospecting of fossil sites developed in fine-grained siliciclastic sequences. These localities contain an exceptionally rich, varied and well-preserved vertebrate fauna together with invertebrate and plant fossils. Carnivore species are strikingly well represented at Batallones 1 and 3, and large herbivore species, such as mastodons, rhinoceros and giraffes, at Batallones 2, 4, 5 and 10. The taphonomical studies, together with the morphological features shown by the sedimentary fills of the mammal localities, permit an overall interpretation of these deposits as vertebrate traps. The study of these localities should offer a significant contribution to our understanding of the formation pattern of trap-like paleontological sites - which so far have been typically reported in karstic-type systems -, as well as an important source of paleobiological information about numerous vertebrate groups.
    Keywords: Mammalia ; miocene ; Cerro de los Batallones
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/bookPart
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