Legionella pneumophila serogroup 3 infection: importance of serology

We present a case of Legionella pneumophila serogroup 3 (LP3) infection in a patient with severe community-acquired pneumonia (CAP). The diagnosis was complicated by an initial equivocal L. pneumophila urinary antigen test, followed by two negative samples. LP3 was cultured from a sputum sample and the diagnosis was confirmed by serology 15 days into the admission. This case highlights the importance of considering non-LP1 serogroups as causes of CAP and the role of serological testing in diagnosis.

Rapid detection, differentiation and typing of methicillin-resistant Staphylococcus aureus harbouring either mecA or the new mecA homologue mecA(LGA251)

The recent finding of a new mecA homologue, mecA(LGA251) , with only 70% nucleotide homology to the conventional mecA gene has brought the routine testing for mecA as a confirmatory test for methicillin-resistant Staphylococcus aureus (MRSA) into question. A multiplex PCR was designed to differentiate mecA(LGA251) from the known mecA together with detection of lukF-PV and the spa gene fragments, enabling direct spa typing by sequencing of the PCR amplicons. The PCR analysis and subsequent spa typing were validated on a large collection (n=185) of contemporary MRSA and methicillin-sensitive S. aureus isolates, including 127 isolates carrying mecA(LGA251) . The mecA(LGA251) gene was situated in staphylococcal cassette chromosome mec type XI elements, and sequence variation within a 631-bp fragment of mecA(LGA251) in 79 isolates indicated a very conserved gene sequence. Following a successful validation, the multiplex PCR strategy was implemented in the routine testing of MRSA for national surveillance. Over a 2-month period, among 203 samples tested, 12 new MRSA cases caused by isolates carrying mecA(LGA251) were identified, emphasizing the clinical importance of testing for these new MRSA isolates.

Intermediate-conductance calcium-activated potassium channels participate in neurovascular coupling

BACKGROUND AND PURPOSE

Controlling vascular tone involves K(+) efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (K(Ca)2.3 and K(Ca)3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling.

EXPERIMENTAL APPROACH

Transgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess K(Ca)2.3 and K(Ca)3.1 expression by immunohistochemistry and RT-PCR. K(Ca) currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of K(Ca)3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry.

KEY RESULTS

K(Ca)3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic K(Ca)2.3 and K(Ca)3.1 mRNA expression. With 200 nM [Ca(2+)](i) , the K(Ca)2.1-2.3/K(Ca)3.1 opener NS309 increased whole-cell currents. CyPPA, a K(Ca)2.2/K(Ca)2.3 opener, was without effect. With 1 µM [Ca(2+)](i) , the K(Ca)3.1 inhibitor TRAM-34 reduced currents whereas apamin (K(Ca)2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing K(Ca)3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of K(Ca)3.1 and the large-conductance K(Ca) channel, K(Ca)1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%.

CONCLUSION AND IMPLICATIONS

Astrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling.

Thiazolides as novel antiviral agents. 2. Inhibition of hepatitis C virus replication

We report the activities of a number of thiazolides [2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis C virus (HCV) genotypes IA and IB, using replicon assays. The structure-activity relationships (SARs) of thiazolides against HCV are less predictable than against hepatitis B virus (HBV), though an electron-withdrawing group at C(5') generally correlates with potency. Among the related salicyloylanilides, the m-fluorophenyl analogue was most promising; niclosamide and close analogues suffered from very low solubility and bioavailability. Nitazoxanide (NTZ) 1 has performed well in clinical trials against HCV. We show here that the 5'-Cl analogue 4 has closely comparable in vitro activity and a good cell safety index. By use of support vector analysis, a quantitative structure-activity relationship (QSAR) model was obtained, showing good predictive models for cell safety. We conclude by updating the mode of action of the thiazolides and explain the candidate selection that has led to compound 4 entering preclinical development.

The vascular extracellular calcium-sensing receptor: an update

The extracellular calcium-sensing receptor (CaR) was first described in the parathyroid gland. Recent studies have shown that the CaR is also expressed in blood vessels, especially in the endothelial and adventitial layers but its physiological function is still not clear. However, an understanding of its possible role(s) in the vasculature (perivascular-neurones, heart and blood vessels) is important because of the use of synthetic positive allosteric CaR modulators in hyperparathyroidism and the potential importance of negative modulators in the treatment of osteoporosis. In this review, the effects of CaR activation and inhibition are detailed and the possible role of the CaR as both an amplifier and attenuator of myo-endothelial coupling in the vasculature is described.

Novel age-dependent learning deficits in a mouse model of Alzheimer's disease: implications for translational research

Computational modeling predicts that the hippocampus plays an important role in the ability to apply previously learned information to novel problems and situations (referred to as the ability to generalize information or simply as 'transfer learning'). These predictions have been tested in humans using a computer-based task on which individuals with hippocampal damage are able to learn a series of complex discriminations with two stimulus features (shape and color), but are impaired in their ability to transfer this information to newly configured problems in which one of the features is altered. This deficit occurs despite the fact that the feature predictive of the reward (the relevant information) is not changed. The goal of the current study was to develop a mouse analog of transfer learning and to determine if this new task was sensitive to pathological changes in a mouse model of AD. We describe a task in which mice were able to learn a series of concurrent discriminations that contained two stimulus features (odor and digging media) and could transfer this learned information to new problems in which the irrelevant feature in each discrimination pair was altered. Moreover, we report age-dependent deficits specific to transfer learning in APP+PS1 mice relative to non-transgenic littermates. The robust impairment in transfer learning may be more sensitive to AD-like pathology than traditional cognitive assessments in that no deficits were observed in the APP+PS1 mice on the widely used Morris water maze task. These data describe a novel and sensitive paradigm to evaluate mnemonic decline in AD mouse models that has unique translational advantages over standard species-specific cognitive assessments (e.g., water maze for rodent and delayed paragraph recall for humans).

Thiazolides as novel antiviral agents. 1. Inhibition of hepatitis B virus replication

We report the syntheses and activities of a wide range of thiazolides [viz., 2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis B virus replication, with QSAR analysis of our results. The prototypical thiazolide, nitazoxanide [2-hydroxybenzoyl-N-(5-nitrothiazol-2-yl)amide, NTZ] 1 is a broad spectrum antiinfective agent effective against anaerobic bacteria, viruses, and parasites. By contrast, 2-hydroxybenzoyl-N-(5-chlorothiazol-2-yl)amide 3 is a novel, potent, and selective inhibitor of hepatitis B replication (EC(50) = 0.33 μm) but is inactive against anaerobes. Several 4'- and 5'-substituted thiazolides show good activity against HBV; by contrast, some related salicyloylanilides show a narrower spectrum of activity. The ADME properties of 3 are similar to 1; viz., the O-acetate is an effective prodrug, and the O-aryl glucuronide is a major metabolite. The QSAR study shows a good correlation of observed EC(90) for intracellular virions with thiazolide structural parameters. Finally we discuss the mechanism of action of thiazolides in relation to the present results.

Intermediate-conductance calcium-activated potassium channels participate in neurovascular coupling

BACKGROUND AND PURPOSE

Controlling vascular tone involves K(+) efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (K(Ca)2.3 and K(Ca)3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling.

EXPERIMENTAL APPROACH

Transgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess K(Ca)2.3 and K(Ca)3.1 expression by immunohistochemistry and RT-PCR. K(Ca) currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of K(Ca)3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry.

KEY RESULTS

K(Ca)3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic K(Ca)2.3 and K(Ca)3.1 mRNA expression. With 200 nM [Ca(2+)](i) , the K(Ca)2.1-2.3/K(Ca)3.1 opener NS309 increased whole-cell currents. CyPPA, a K(Ca)2.2/K(Ca)2.3 opener, was without effect. With 1 µM [Ca(2+)](i) , the K(Ca)3.1 inhibitor TRAM-34 reduced currents whereas apamin (K(Ca)2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing K(Ca)3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of K(Ca)3.1 and the large-conductance K(Ca) channel, K(Ca)1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%.

CONCLUSION AND IMPLICATIONS

Astrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling.

The binding of the antimalarial arteether to human plasma proteins in-vitro

The binding of the novel antimalarial drug, arteether, to human plasma, pure albumin and α1-acid glycoprotein has been investigated by ultrafiltration, using [14C]arteether. The protein binding in plasma obtained from 11 healthy male subjects ranged from 73·4 to 81·8% bound, with a mean of 78·7 ± 2·1%. The binding of drug in plasma was mainly accounted for by binding to albumin and α1-acid glycoprotein. Scatchard analysis of the binding data revealed that the binding affinity of arteether to α1-acid glycoprotein is much greater (20-fold) than that to albumin. This suggests that α1-acid glycoprotein is the more important binding protein in plasma. This may have clinical importance due to alterations in plasma protein binding in patients with malaria, as the concentration of α1-acid glycoprotein is markedly increased during malarial infection.

Impairment of endothelial SK(Ca) channels and of downstream hyperpolarizing pathways in mesenteric arteries from spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Previous studies have shown that endothelium-dependent hyperpolarization of myocytes is reduced in resistance arteries from spontaneously hypertensive rats (SHRs). The aim of the present study was to determine whether this reflects down-regulation of endothelial K(+) channels or their associated pathways.

EXPERIMENTAL APPROACH

Changes in vascular K(+) channel responses and expression were determined by a combination of membrane potential recordings and Western blotting.

KEY RESULTS

Endothelium-dependent myocyte hyperpolarizations induced by acetylcholine, 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309) (opens small- and intermediate-conductance calcium-sensitive K(+) channels, SK(Ca) and IK(Ca), respectively) or cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (SK(Ca) opener) were reduced in mesenteric arteries from SHRs. After blocking SK(Ca) channels with apamin, hyperpolarizations to acetylcholine and NS309 in SHR arteries were similar to those of controls. Hyperpolarization to 5 mM KCl was reduced in SHR arteries due to loss of the Ba(2+)-sensitive, inward-rectifier channel (K(IR)) component; the contribution of ouabain-sensitive, Na(+)/K(+)-ATPases was unaffected. Protein expression of both SK(Ca) and K(IR) channels was reduced in SHR arteries; the caveolin-1 monomer/dimer ratio was increased.

CONCLUSIONS AND IMPLICATIONS

In SHRs, the distinct pathway that generates endothelium-dependent hyperpolarization in vascular myocyte by activation of IK(Ca) channels and Na(+)/K(+)-ATPases remains intact. The second pathway, initiated by endothelial SK(Ca) channel activation and amplified by K(IR) opening on both endothelial cells and myocytes is compromised in SHRs due to down-regulation of both SK(Ca) and K(IR) and to changes in caveolin-1 oligomers. These impairments in the SK(Ca)-K(IR) pathway shed new light on vascular control mechanisms and on the underlying vascular changes in hypertension.