Search results for "Quaternary"

Exercise and recovery in frog muscle: metabolism of PCr, adenine nucleotides, and related compounds

1996

The effects of exercise (swimming), fatigue, and recovery on the intracellular pH (pHi), energy-rich phosphates, and related metabolites were studied in the gastrocnemius muscle of common frogs (Rana temporaria) at 20 degrees C. Exercise caused a rapid decrease in the content of phosphocreatine (PCr) and a corresponding increase in that of Pi. The ATP level remained virtually constant for 1 min; its precipitous decrease during the following minute was associated with a rise in the contents of inosine 5'-monophosphate (IMP) and NH4+, indicating a marked activation of AMP deaminase. Five minutes of swimming caused severe fatigue, which was correlated with decreases in muscle PCr (-85%), ATP …

The use of the de deckere-ten hoor preparation for study of nicotinic and potassium-evoked dopamine ?-hydroxylase release from the rabbit heart

1980

1. Dopamine β-hydroxylase (DBH) and noradrenaline were determined both in the venous effluent (perfusate) and in the transmyocardial fluid (TMF) collected from the apex of the rabbit isolated heart which was prepared according to De Deckere and Ten Hoor (1977) and perfused with Tyrode's solution at 20 ml/min. 2. Perfusion for 2 min with the nicotinic drug, p-aminophenethyl-trimethylammonium (PAPETA), both in the absence of presence of atropine evoked noradrenaline overflow into the perfusate and TMF that was maximal in the 0–2 min sample and declined from maximum with a t1/2 of 0.6 min. DBH was released into TMF with the maximum from 2–4 min and a t1/2 of decline of 5.6 min. 3. High K-low N…

The effects of methacholine and calcium deprivation on the release of the false transmitter, ?-methyladrenaline, from the isolated rabbit heart

1976

1. Anaesthetized rabbits were infused for 20 min with 85 μg · kg−1 · min−1 (±)-α-methyladrenaline. The hearts dissected 15 min after the infusion contained 1.49 μg/g α-methyladrenaline; the endogenous noradrenaline content was correspondingly decreased. 2. Hearts from α-methyladrenaline-infused animals were isolated with the right sympathetic nerves intact and perfused. Ventricular rate, right atrial and right ventricular tensions were recorded using the transverse method. 3. Electrical stimulation (10 Hz, 1 ms, 1 min) of sympathetic nerves, perfusion with the nicotinic drug, p-aminophenethyltrimethylammonium (PAPETA) or perfusion with 54 mM KCl (high K+) solution evoked an output of both α…

The story of endurance:Biogeography and the evolutionary history of four Holarctic butterflies with different habitat requirements

2021

Aim: Biogeographical studies on the entire ranges of widely distributed species can change our perception of species’ range dynamics. We studied the effects of Pleistocene glacial cycles on current butterfly species distributions, aiming to uncover complex biogeographic patterns in the Holarctic, a region dramatically affected by Cenozoic climate change. Location: Eurasia and North America. Taxon: Boloria chariclea, Agriades optilete, Carterocephalus palaemon, Oeneis jutta. Methods: We reconstructed the biogeographic history of four butterfly species differing in habitat preferences (B. chariclea – tundra, A. optilete – bogs, C. palaemon – temperate grasslands, O. jutta – taiga), using one …

Late Quaternary environments in the Gobi Desert of Mongolia: Vegetation, hydrological, and palaeoclimate evolution

2019

Abstract Considerable efforts have been devoted to decipher the late Quaternary moisture and thermal evolution of arid central Asia. However, disparate interpretations still exist concerning different proxies. The spatial and temporal heterogeneities have inhibited a holistic understanding of general patterns and underlying mechanisms. To address these issues, two parallel cores (ONW I, 6.00 m; ONW II, 13.35 m) were retrieved in the Gobi Desert of Mongolia from lake Orog Nuur. Multidisciplinary investigations including geomorphological mapping, radiocarbon dating, sedimentological, palynological and ostracod analyses enabled us to gain a comprehensive dataset for vegetation development and …

A stalactite record of four relative sea-level highstands during the Middle Pleistocene Transition

2017

International audience; Ice-sheet and sea-level fluctuations during the Early and Middle Pleistocene are as yet poorly understood. A stalactite from a karst cave in North West Sicily (Italy) provides the first evidence of four marine inundations that correspond to relative sea-level highstands at the time of the Middle Pleistocene Transition. The speleothem is located ∼97 m above mean sea level as result of Quaternary uplift. Its section reveals three marine hiatuses and a coral overgrowth that fixes the age of final marine ingression at 1.124 ± 0.2, thus making this speleothem the oldest stalactite with marine hiatuses ever studied to date. Scleractinian coral species witness light-limited…

Palaeoenvironments and Quaternary foraminifera in the Elx coastal lagoon (Alicante, Spain)

2010

Abstract During the Quaternary, different palaeoenvironments characterised the Elx coastal lagoon (‘Albufera d'Elx’) located in the easternmost sector of the Betic Ranges (SE Spain). Micropalaeontological and sedimentological analysis of three drilled cores allowed characterization of different sedimentary environments, including alluvial, restricted lagoon, lagoon with marine connection, shoreface, foreshore, backshore, swamp, washover fan, and back-barrier flat. A model of the evolution of this region during Marine Isotope Stage (MIS) 7 is proposed, based on chronostratigraphic correlation between the cores. Up to six transgressive episodes can be recognised, mostly represented by calcare…

Properties of the quaternary half-metal-type Heusler alloyCo2Mn1−xFexSi

2006

This paper reports on the bulk properties of the quaternary Heusler alloy Co2Mn1�xFexSi with the Fe concentration x =0,1/2,1. All samples, which were prepared by arc melting, exhibit L21 long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co2Mn1�xFexSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, Mossbauer spectroscopy, and differential scanning calorimetry. The electronic structure was explored by means of highenergy photoemission spectroscopy at about 8 keV photon energy. This ensures true bulk sensitivity of the measurements. The magnetization of the Fe-doped Heusler alloys …

Photoluminescence of chromium(III)-doped silicoaluminophosphate with AFI structure

1994

Tracking the structural dynamics of proteins in solution using time-resolved wide-angle X-ray scattering

2008

We demonstrate tracking of protein structural changes with time-resolved wide-angle X-ray scattering (TR-WAXS) with nanosecond time resolution. We investigated the tertiary and quaternary conformational changes of human hemoglobin under nearly physiological conditions triggered by laser-induced ligand photolysis. We also report data on optically induced tertiary relaxations of myoglobin and refolding of cytochrome c to illustrate the wide applicability of the technique. By providing insights into the structural dynamics of proteins functioning in their natural environment, TR-WAXS complements and extends results obtained with time-resolved optical spectroscopy and X-ray crystallography.