Calculation of pulsatile flow and particle paths in an aneurysm-model

Summary The velocity field and the wall shear stress have been calculated numerically by the finite element method to the time-dependent Navier-Stokes equations for pulsatile flow in a model of an aneurysm. The results show a complex flow field with two eddies growing and disappearing during the cardiac cycle. Downstream at the outlet vessel high wall shear stress occurs, which may lead to a downstream-growing of the aneurysm.With the knowledge of a sufficiently accurate flow field, the calculation of several particle paths has been carried out. Starting points and starting time are varied. The paths demonstrate the time-dependent development, shift and disappearance of vortices during the pulsatile cycle and provide hints on zones of stasis. These are significant factors in thrombogenesis.Supported by the Fonds zur Förderung der wissenschaftlichen Forschung, project number P4671     

AMP-activated protein kinase regulates hERG potassium channel

Besides their role in cardiac repolarization, human ether-a-go-go-related gene potassium (hERG) channels are expressed in several tumor cells including rhabdomyosarcoma cells. The channels foster cell proliferation. Ubiquitously expressed AMP-dependent protein kinase (AMPK) is a serine-/threonine kinase, stimulating energy-generating and inhibiting energy-consuming processes thereby helping cells survive periods of energy depletion. AMPK has previously been shown to regulate Na⁺/K⁺ ATPase, Na⁺/Ca²⁺ exchangers, Ca²⁺ channels and K⁺ channels. The present study tested whether AMPK regulates hERG channel activity. Wild type AMPK (α1β1γ1), constitutively active ^γR70QAMPK (α1β1γ1(R70Q)), or catalytically inactive ^αK45RAMPK (α1(K45R)β1γ1) were expressed in Xenopus oocytes with hERG. Tail currents were determined as a measure of hERG channel activity by two-electrode-voltage clamp. hERG membrane abundance was quantified by chemiluminescence and visualized by immunocytochemistry and confocal microscopy. Moreover, hERG currents were measured in RD rhabdomyosarcoma cells after pharmacological modification of AMPK activity using the patch clamp technique. Coexpression of wild-type AMPK and of constitutively active ^γR70QAMPK significantly downregulated the tail currents in hERG-expressing Xenopus oocytes. Pharmacological activation of AMPK with AICAR or with phenformin inhibited hERG currents in Xenopus oocytes, an effect abrogated by AMPK inhibitor compound C. ^γR70QAMPK enhanced the Nedd4-2-dependent downregulation of hERG currents. Coexpression of constitutively active ^γR70QAMPK decreased membrane expression of hERG in Xenopus oocytes. Compound C significantly enhanced whereas AICAR tended to inhibit hERG currents in RD rhabdomyosarcoma cells. AMPK is a powerful regulator of hERG-mediated currents in both, Xenopus oocytes and RD rhabdomyosarcoma cells. AMPK-dependent regulation of hERG may be particularly relevant in cardiac hypertrophy and tumor growth.     

Downregulation of the renal outer medullary K+ channel ROMK by the AMP-activated protein kinase

The 5′-adenosine monophosphate-activated serine/threonine protein kinase (AMPK) is stimulated by energy depletion, increase in cytosolic Ca²⁺ activity, oxidative stress, and nitric oxide. AMPK participates in the regulation of the epithelial Na⁺ channel ENaC and the voltage-gated K⁺ channel KCNE1/KCNQ1. It is partially effective by decreasing PIP₂ formation through the PI3K pathway. The present study explored whether AMPK regulates the renal outer medullary K⁺ channel ROMK. To this end, cRNA encoding ROMK was injected into Xenopus oocytes with and without additional injection of constitutively active AMPK^γR70Q (AMPK^α1-HA+AMPK^β1-Flag+AMPKγ1^R70Q), or of inactive AMPK^αK45R (AMPK^α1K45R+AMPK^β1-Flag+AMPK^γ1-HA), and the current determined utilizing two-electrode voltage-clamp and single channel patch clamp. ROMK protein abundance was measured utilizing chemiluminescence in Xenopus oocytes and western blot in whole kidney tissue. Moreover, renal Na⁺ and K⁺ excretion were determined in AMPK^α1-deficient mice (ampk ^?/? ) and wild-type mice (ampk ^+/+ ) prior to and following an acute K⁺ load (111 mM KCl, 30 mM NaHCO₃, 4.7 mM NaCl, and 2.25 g/dl BSA) at a rate of 500 μl/h. As a result, coexpression of AMPK^γR70Q but not of AMPK^αK45R significantly decreased the current in ROMK1-expressing Xenopus oocytes. Injection of phosphatidylinositol PI_(4,5)P₂ significantly increased the current in ROMK1-expressing Xenopus oocytes, an effect reversed in the presence of AMPK^γR70Q. Under control conditions, no significant differences between ampk ^?/? and ampk ^+/+ mice were observed in glomerular filtration rate (GFR), urinary flow rate, serum aldosterone, plasma Na⁺, and K⁺ concentrations as well as absolute and fractional Na⁺ and K⁺ excretion. Following an acute K⁺ load, GFR, urinary flow rate, serum aldosterone, plasma Na⁺, and K⁺ concentration were again similar in both genotypes, but renal absolute and fractional Na⁺ and K⁺ excretion were higher in ampk ^?/? than in ampk ^+/+ mice. According to micropuncture following a K⁺ load, delivery of Na⁺ to the early distal tubule but not delivery of K⁺ to late proximal and early distal tubules was increased in ampk ^?/? mice. The upregulation of renal ROMK1 protein expression by acute K⁺ load was more pronounced in ampk ^?/? than in ampk ^+/+ mice. In conclusion, AMPK downregulates ROMK, an effect compromising the ability of the kidney to excrete K⁺ following an acute K⁺ load.     

Characterization of the anti‐HBV activity of HLP1–23, a human lactoferrin‐derived peptide

Lactoferrin (Lf) was shown to exhibit its antiviral activity at an early phase of viral infection and a mechanism whereby the protein interacts with host cell surface molecules has been suggested. In this study, human Lf (HLf) and seven HLf‐derived synthetic peptides (HLP) corresponding to the N‐terminal domain of the native protein (1–47 amino acids sequence) were assayed for their capacity to prevent hepatitis B virus (HBV) infection and replication using the HepaRG and HepG2.2.2.15 cell lines. Of the series tested, four peptides showed 40–75% inhibition of HBV infection in HepaRG cells, HLP_1–23, containing the GRRRR cationic cluster, being the most potent. Interestingly, this cluster is one of the two glycosaminoglycan binding sites of the native HLf involved in its antiviral activity; however, the mechanism of the HLP_1–23 action was different from that of the full‐length protein, the peptide inhibiting HBV infection when pre‐incubated with the virus, while no effect was observed on the target cells. It is suggested that the cationic cluster is sufficient for the peptide to interact stably with negatively charged residues on the virion envelope, while the absence of the second glycosaminoglycan binding site prevents its efficient attachment to the cells. In conclusion, this peptide may constitute a non‐toxic approach for potential clinical applications in inhibiting HBV entry by neutralizing the viral particles. J. Med. Virol. 85:780–788, 2013. © 2013 Wiley Periodicals, Inc.     

A socio-ecological analysis of risk,protective and promotive factors for the mental health of Burundian refugee children living in refugee camps

European Child & Adolescent Psychiatry - Children and adolescents’ mental health risk and resilience arise from a complex interplay of factors on several socio-ecological levels. However,...     

Comments on “Evaluation and review of ways to differentiate sources of ethanol in post-mortem blood”

International Journal of Legal Medicine -     

Extended stereotactic brain biopsy in suspected primary central nervous system angiitis: good diagnostic accuracy and high safety

Journal of Neurology - To evaluate the diagnostic accuracy and safety of extended stereotactic brain biopsy (ESBB) in a single center cohort with suspected primary angiitis of the central nervous...     

COVID-19 or not COVID-19? Compared characteristics of patients hospitalized for suspected COVID-19

European Journal of Clinical Microbiology & Infectious Diseases - During an epidemic period, we compared patients hospitalized for initial suspicion of COVID-19 but for whom an alternative...