Scattered populations of Rüppell’s foxes (Vulpes rueppelli) occur across the deserts of northern Africa and Arabia. Little is known about the biology of these canids, especially the physiological ...mechanisms that contribute to their ability to live in such harsh environments. For individuals from Saudi Arabia, we tested the hypotheses that Rüppell’s foxes have a reduced basal metabolic rate and total evaporative water loss (TEWL), parameters measured in the laboratory, and a reduced field metabolic rate (FMR) and water flux when free‐living. Under basal conditions in the laboratory, males, which averaged 1,858 g in body mass, had an oxygen consumption of 914.9 mL O2/h, whereas females, which weighed on average 1,233 g, consumed 682.9 mL O2/h; rates of oxygen consumption translated to 441.4 kJ/d and 329.4 kJ/d, respectively. TEWL averaged 52.6 g H2O/d for males and 47.5 g H2O/d for females. We found no evidence that basal metabolism is reduced in Rüppell’s foxes, but their TEWL was remarkably low: 50.9% of allometric prediction for males and 64.5% for females. In the wild during winter, males expended energy at a rate of 1,306.5 kJ/d, whereas females had an expenditure of 722.8 kJ/d. Analysis of covariance with FMR as the dependent variable, sex as a fixed factor, and body mass as a covariate showed no statistical difference in FMR between sexes. Water flux did not differ significantly between sexes and averaged 123 mL H2O/d, a value 30% lower than the kit fox from the deserts of southwestern North America. FMR was positively related to nocturnal activity levels as
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackageOT2,OT1{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{FMR}\,\,( \mathrm{kJ}\,/ \mathrm{d}\,) =-2,900.1+55.5$ \end{document}
(% of time moving). The water content of prey items varied between 1.9 and 4.1 g H2O/g dry matter consumed. Based on these values and knowledge of their diet, we calculated that foxes captured about one rodent and a variety of anthropods per night of foraging.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The microscopic properties of water in narrow pores are relevant to the function of ion channels and related membrane transport proteins. The emergence of several high-resolution structures allows ...one to perform molecular dynamics simulation studies of water in such pores. Simulations of bundles of parallel alpha-helical peptides (e.g. alamethicin) have enabled development of methodologies and concepts appropriate to such investigations. In the narrow channels formed by such bundles, water molecules exhibit reduced rotational and translation motion. This reduction in water mobility may be a general property of narrow pores. We have used simplified channel models to explore the role of hydrophobicity/hydrophilicity in the entry of water into pores. Narrow pores with a hydrophobic lining, although physically open, may not admit water molecules, acting as a 'hydrophobic gate' that prevents water and ion permeation. Such a gate can be opened either by widening the pore or making its lining more polar. Simulations have been used to explore the behaviour of water in GlpF, a member of the aquaporin family of water pores, and OmpA, a bacterial outer membrane protein. Preliminary results suggest that a continuous water wire is not formed within the amphipathic GlpF pore. Simulations of OmpA, in which polar residues line the channel, indicate that a small conformational change in one of the channel lining side chains may open the channel. In summary, comparison of the behaviour of water in different narrow transmembrane pores suggests that an amphipathic pore is ideal for water permeation, and that either a highly hydrophobic pore lining or a charged pore-lining region can act as a gate.
We report here the first genome sequence of the white-rot fungus Obba rivulosa (Polyporales, Basidiomycota), a polypore known for its lignin-decomposing ability. The genome is based on the homokaryon ...3A-2 originating in Finland. The genome is typical in size and carbohydrate active enzyme (CAZy) content for wood-decomposing basidiomycetes.
Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so‐called electrical remodeling of the atria (ERA) ...and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP430 ms at 7.4 ± 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time‐ and frequency‐domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 ± 5.6 to 102 ± 6.4 ms, P < 0.0001). No significant changes in HRV and dispersion of refractoriness (ΔAERP) (47 ± 7.1 to 44 ± 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 ± 6.4 to 135 ± 8.8 ms, P < 0.0001) and was paralleled by a significant increase in ΔAERP (44 ± 4.2 to 63 ± 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 ± 6.5 versus 43.0 ± 5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 ± 4.0 versus 42.5 ± 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P < 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and ΔAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.
Gene Expression in Human Atrial Fibrillation. Introduction: Atrial fibrillation (AF) leads to a loss of atrial contraction within hours to days. During persistence of AF, cellular dedifferentiation ...and hypertrophy occur, eventually resulting in degenerative changes and cell death. Abnormalities in the calcium handling in response to tachycardia‐induced intracellular calcium overload play a pivotal role in these processes.
Methods and Results: The purpose was to investigate the mRNA expression of proteins and ion channels influencing the calcium handling in patients with persistent AF. Right atrial appendages were obtained from 18 matched controls in sinus rhythm (group 1) and 18 patients with persistent AF undergoing elective cardiac surgery. Previous duration of AF was ≥ 6 months in 9 (group 2) and > 6 months in 9 patients (group 3). In a single semiquantitative polymerase chain reaction, the mRNA of interest and of glyceraldehydes‐3‐phosphate dehydrogenase, were coamplified and separated by gel electrophoresis. L‐type calcium channel α, subunit mRNA content was inversely related to the duration of AF: −26% in group 2 compared to group 1 (P = 0.2), and −49% in group 3 compared to group 1 (P = 0.01). Inhibitory guanine nucleotide binding protein iα2 mRNA content was reduced in group 3 compared to group 1 (−30%, P = 0.01). Sarcoplasmic reticulum calcium ATPase, phospholamban and sodiumcalcium exchanger mRNA contents were not affected by AF.
Conclusions: AF‐induced alterations in mRNA contents of proteins and ion channels involved in the calcium handling seem to occur in relation to the previous duration of AF. In the present patient population, these changes were significant only if AF lasted > 6 months.
Alamethicin is a 20-residue channel-forming peptide that forms a stable amphipathic alpha-helix in membrane and membrane-mimetic environments. This helix contains a kink induced by a central ...Gly-X-X-Pro sequence motif. Alamethicin channels are activated by a cis positive transbilayer voltage. Channel activation is suggested to correspond to voltage-induced insertion of alamethicin helices in the bilayer. Alamethicin forms multi-conductance channels in lipid bilayers. These channels are formed by parallel bundles of transmembrane helices surrounding a central pore. A change in the number of helices per bundle switches the single channel conductance level. Molecular dynamics simulations of alamethicin in a number of different environments have been used to explore its channel-forming properties. These simulations include: (i) alamethicin in solution in water and in methanol; (ii) a single alamethicin helix at the surface of a phosphatidylcholine bilayer; (iii) single alamethicin helices spanning a phosphatidylcholine bilayer; and (iv) channels formed by bundles of 5, 6, 7 or 8 alamethicin helices spanning a phosphatidylcholine bilayer. The total simulation time is c. 30 ns. Thus, these simulations provide a set of dynamic snapshots of a possible mechanism of channel formation by this peptide.
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