Visualizing physiological parameters in cells and tissues using genetically encoded indicators for metabolites.

The study of metabolism is undergoing a renaissance. Since the year 2002, over 50 genetically-encoded fluorescent indicators (GEFIs) have been introduced, capable of monitoring metabolites with high spatial/temporal resolution using fluorescence microscopy. Indicators are fusion proteins that change their fluorescence upon binding a specific metabolite. There are indicators for sugars, monocarboxylates, Krebs cycle intermediates, amino acids, cofactors, and energy nucleotides. They permit monitoring relative levels, concentrations, and fluxes in living systems. At a minimum they report relative levels and, in some cases, absolute concentrations may be obtained by performing ad hoc calibration protocols. Proper data collection, processing, and interpretation are critical to take full advantage of these new tools. This review offers a survey of the metabolic indicators that have been validated in mammalian systems. Minimally invasive, these indicators have been instrumental for the purposes of confirmation, rebuttal and discovery. We envision that this powerful technology will foster metabolic physiology.

Nanometer-resolved quantification of mechanical response in nanoparticle-based composites.

Nanocomposites constitute an upcoming class of materials that has enormous potential within a broad range of areas, particularly with regard to mechanical applications. However, the tuning of material properties requires a full understanding of the mechanical response of the nanocomposite across all length scales. While characterization from the micro to macroscale is well established at this point, quantification of mechanical behavior at the nanoscale is still an unresolved challenge. With this background, the current work demonstrates the capabilities of quantitative contact resonance atomic force microscopy (CR-AFM) to localize and reliably characterize Ni nanoparticles that are embedded below the surface of thermally oxidized silicon thin films. Correlating these results with numerical simulations as well as high-resolution transmission electron microscopy measurements provides a comprehensive understanding of the subtle interplay between the structure and nanomechanical response of the composite.

Small is fast: astrocytic glucose and lactate metabolism at cellular resolution.

Brain tissue is highly dynamic in terms of electrical activity and energy demand. Relevant energy metabolites have turnover times ranging from milliseconds to seconds and are rapidly exchanged between cells and within cells. Until recently these fast metabolic events were inaccessible, because standard isotopic techniques require use of populations of cells and/or involve integration times of tens of minutes. Thanks to fluorescent probes and recently available genetically-encoded optical nanosensors, this Technology Report shows how it is now possible to monitor the concentration of metabolites in real-time and in single cells. In combination with ad hoc inhibitor-stop protocols, these probes have revealed a key role for K(+) in the acute stimulation of astrocytic glycolysis by synaptic activity. They have also permitted detection of the Warburg effect in single cancer cells. Genetically-encoded nanosensors currently exist for glucose, lactate, NADH and ATP, and it is envisaged that other metabolite nanosensors will soon be available. These optical tools together with improved expression systems and in vivo imaging, herald an exciting era of single-cell metabolic analysis.

[Corynebacterium diphtheriae endocarditis complicated by septic arthritis and cerebral abscess]. / Endocardite à Corynebacterium diphtheriae compliquée d'arthrites septiques et d'abcès cérébral.

The authors report a rare case of the mitis type Corynebacterium diphteriae endocarditis on a prosthetic valve complicated by septic arthritis and cerebral abscess. The authors underline the importance of regular transoesophageal echocardiographic control and underline the diagnostic value of ultrafast computed tomography for the diagnosis of aortic annular and interventricular septal abscesses in patients with mechanical prosthetic valves.

Bartonella (Rochalimaea) quintana endocarditis in three homeless men.

BACKGROUND: Bartonella (Rochalimaea) quintana is the agent of trench fever and is transmitted by the body louse. We searched for this organism in three alcoholic homeless men with endocarditis. METHODS: Blood samples were cultured on a human endothelial cell line and on blood agar. Bacteria were identified by sequencing the amplified 16S ribosomal RNA gene. The presence of bartonella in tissue was assessed by Gram's staining, immunostaining, and polymerase-chain-reaction amplification. Serologic studies for antibodies to bartonella species were performed by indirect immunofluorescence and Western immunoblotting. RESULTS: B. quintana was isolated from one patient in the blood-agar culture and from the other two patients in the endothelial-cell culture. The organism was also identified by both immunostaining and molecular techniques in the valvular vegetations from the three patients and in a cervical lymph node from one patient. The 16S ribosomal RNA gene sequences of the three isolates were almost identical to that of the prototype strain of B. quintana. High titers of antibodies to B. quintana were detected in all three patients, but so were cross-reacting antibodies to chlamydia species. In all three patients studies were repeatedly negative for antibodies to the human immunodeficiency virus. CONCLUSIONS: B. quintana is a cause of endocarditis in homeless patients and may be serologically misdiagnosed as a chlamydial infection.

[Struma cordis: right intraventricular ectopic thyroid]. / Struma cordis: Thyroïde ectopique intraventriculaire droite.

The authors report the case of a benign tumour composed of hyperplasic thyroid tissue in the right ventricle, diagnosed in a 43 year old woman by echocardiography after a syncopal episode. The outcome was favourable with a 13 year follow-up after surgery.

[Left coronaro-ventricular fistula after septal myectomy]. / Fistule coronaro-ventriculaire gauche après myectomie septale.

The authors report the case of a 17 year old patient operated for valvular aortic stenosis associated with severe hypertrophy of the interventricular septum. The operation consisted of aortic valve replacement and septal myectomy. Color-flow imaging in the postoperative period showed a coronary artery--left ventricular fistula in the region of the septal myectomy. In view of the small size of the fistula on echocardiographic examination and the absence of a codified strategy of management of acquired coronary left ventricular fistula after surgery, a simple Doppler echocardiographic follow-up was proposed in this case.