Apolipoprotein B is a new target of the GDNF/RET and ET-3/EDNRB signalling pathways

BACKGROUND

GDNF/RET and Endothelin-3 (ET-3)/EDNRB regulate survival, differentiation, migration, and proliferation of neural crest-derived cells. Although several RET and EDNRB signalling mediators have been characterized, most of the genes targeted by these two pathways are still largely unknown. We focused our study on apolipoprotein B (APOB) as a novel target gene of the RET and EDNRB pathways, based on previous data obtained using a Caenorhabditis elegans strain mutant for the homologue of mammalian ECE1.

METHODS

Molecular and cellular studies of Apob were performed in the murine Neuro2a cells, an in vitro model for studying neural crest-derived cell development, along with a mouse knock-in for the Hirschsprung-associated mutation Ret(C620R). Silencing for Apob and Ret has been performed via shRNA.

KEY RESULTS

GDNF/RET and ET-3/EDNRB cooperated in inducing neuronal differentiation resulting in Apob activation in Neuro2a cell line. Apob expression was downregulated in mouse embryos homozygous for the Ret(C620R) mutation and presenting a severe Hirschsprung phenotype. Ret silencing prevented Apob expression increase. MAPK P38 kinase activation evoked Apob expression via GDNF/RET signalling in Neuro2a cells. A p53-dependent repressor element in Apob promoter resulted in a reduced Apob expression. Silencing of Apob reduced HuD protein expression.

CONCLUSIONS & INFERENCES

Apob is a novel downstream target of the RET/EDNRB pathways with a role in neuronal survival and maintenance, as indicated by its effect on HuD expression. Our data provide a conceptual framework to investigate and establish the role of APOB gene in severe gut dysmotility.

Respiratory and cardiac function in congenital muscular dystrophies with alpha dystroglycan deficiency

The aim of this retrospective study was to assess respiratory and cardiac function in a large cohort of patients with congenital muscular dystrophies (CMD) with reduced glycosylation of alphadystroglycan (α-DG). Thirteen of the 115 patients included in the study died between the age of 1 month and 20 years. The age at last follow up of the surviving 102 ranged between 1 year and 68 years (median: 9.3 years). Cardiac involvement was found in 7 of the 115 (6%), 5 with dilated cardiomyopathy, 1 cardiac conductions defects and 1 mitral regurgitation. Respiratory function was impaired in 14 (12%). Ten of the 14 required non invasive nocturnal respiratory support, while the other four required invasive ventilation. Cardiac or respiratory involvement was found in patients with mutations in FKRP, POMT1, POMT2. All of the patients in whom mutation in POMGnT1 were identified had normal cardiac and respiratory function.

Microglial microvesicle secretion and intercellular signaling

Microvesicles (MVs) are released from almost all cell brain types into the microenvironment and are emerging as a novel way of cell-to-cell communication. This review focuses on MVs discharged by microglial cells, the brain resident myeloid cells, which comprise ∼10–12% of brain population. We summarize first evidence indicating that MV shedding is a process activated by the ATP receptor P2X₇ and that shed MVs represent a secretory pathway for the inflammatory cytokine IL-β. We then discuss subsequent findings which clarify how IL-1 β can be locally processed and released from MVs into the extracellular environment. In addition, we describe the current understanding about the mechanism of P2X₇-dependent MV formation and membrane abscission, which, by involving sphingomyelinase activity and ceramide formation, may share similarities with exosome biogenesis. Finally we report our recent results which show that microglia-derived MVs can stimulate neuronal activity and participate to the propagation of inflammatory signals, and suggest new areas for future investigation.

Second-harmonic generation in silicon waveguides strained by silicon nitride

Silicon photonics meets the electronics requirement of increased speed and bandwidth with on-chip optical networks. All-optical data management requires nonlinear silicon photonics. In silicon only third-order optical nonlinearities are present owing to its crystalline inversion symmetry. Introducing a second-order nonlinearity into silicon photonics by proper material engineering would be highly desirable. It would enable devices for wideband wavelength conversion operating at relatively low optical powers. Here we show that a sizeable second-order nonlinearity at optical wavelengths is induced in a silicon waveguide by using a stressing silicon nitride overlayer. We carried out second-harmonic-generation experiments and first-principle calculations, which both yield large values of strain-induced bulk second-order nonlinear susceptibility, up to 40 pm V(-1) at 2,300 nm. We envisage that nonlinear strained silicon could provide a competing platform for a new class of integrated light sources spanning the near- to mid-infrared spectrum from 1.2 to 10 μm.

Changes in Microvascular Blood Flow during Coupled Plasma Filtration and Adsorption

A 51-year-old man with septic shock underwent three consecutive sessions of coupled plasma filtration-adsorption each lasting 12 hours. Sublingual microvascular perfusion was assessed using the orthogonal polarisation spectral imaging technique at three different times: immediate pre-coupled plasma filtration-adsorption phase, two hours following commencement and two hours after its termination. The video images of the sublingual microcirculation were analysed by an investigator blinded to the time of image acquisition. The De Backer's score was calculated. During the coupled plasma filtration-adsorption, the number of perfused vessels increased compared with the pre-coupled plasma filtration-adsorption period, but decreased again after its termination. It is arguable that the elimination of septic mediators during the procedure could account for the observed variations.

Comparison between immunoradiometric and fluorimetric brain natriuretic peptide determination in patients with congestive heart failure

This study compared two different methods, namely the immunoradiometric (IRMA) and fluorimetric (FIA), in order to determine plasma brain natriuretic peptide (BNP) in congestive heart failure (CHF) patients.

METHODS

CHF in-patients underwent echocardiography and plasma BNP determination using both two methods. The echocardiograms analysed left ventricular end-systolic (LVESV) and end-diastolic (LVEDV) volumes and systolic dysfunction [left ventricular ejection fraction (LVEF) <50%].

RESULTS

Seventy-three (71% males, age 67 ± 9.6 yr) patients were enrolled, 31.5% affected by valvular heart disease. The mean LVEF was 39.8 ± 14.1%; in 26 (35%) a hypertensive etiology emerged. The immunoradiometric assay (IRMA) BNP was found to be significantly lower than the FIA determination 116.5 ± 149 pg/ml vs 267.3 ± 285.6 pg/ml; p=0.0001) and the two methods were closely correlated (r=0.89; p=0.00001). Logistic regression demonstrated a significant correlation between BNP, LVEF, and LVESV/LVEDV (r=-0.45, p=0.0003; r=-0.48, p=0.00001; r=0.22 p=0.003; r=0.34 p=0.0001; r=0.13 p=0.02; r=0.28 p=0.001 IRMA and FIA, respectively). IRMA BNP and FIA BNP significantly increased according to the worsening functional class [from 34.3 ± 60.2 pg/ml in NYHA (New York Heart Association) I to 555.5 ± 273.1 pg/ml in NYHA IV; from 86.1 ± 162.1 pg/ml in NYHA I to 1070 ± 42.2 pg/ml in NYHA IV, respectively]. In severe systolic dysfunction (LVEF<30%), receiver operating characteristic analysis revealed a satisfactorily sensitivity and specificity using a cut-off point of 50.6 pg/ml with IRMA and 243 pg/ml with FIA. In mild systolic dysfunction (LVEF<50%), a good sensitivity and specificity using a cut-off point of 42 pg/ml with IRMA and 182 pg/ml with FIA emerged.

CONCLUSIONS

In CHF patients both BNP methods correlated with NYHA class, LVEF, and ventricular volumes.

Robotic transabdominal kidney transplantation in a morbidly obese patient

Kidney transplantation in morbidly obese patients can be technically demanding. Furthermore, morbidly obese patients experience a high rate of wound infections and related complications, which mostly result from the longer length and extent of the incision. These complications can be avoided through minimally invasive surgery; however, conventional laparoscopic instruments are unsuitable for the safe performance of a kidney transplant in morbidly obese patients. Herein, we report the first minimally invasive, total robotic kidney transplant in a morbidly obese patient. A left, deceased donor kidney was transplanted into a 29-year-old woman with a body mass index (BMI) of 41 kg/m(2) who had been on hemodialysis for 5 years. The operation was performed intraabdominally using the DaVinci Robotic Surgical System with 4 trocars and a 7 cm midline incision. The operative time was 223 min, and the blood loss was less than 50 cc. The kidney had immediate graft function. No perioperative complications were observed, and the patient was discharged on postoperative day 5 with normal kidney function. Minimally invasive access and robotic technology facilitated the safe performance of a successful kidney transplant in a morbidly obese patient.

Modified perineal stapled rectal resection with Contour Transtar for full-thickness rectal prolapse

OBJECTIVE

We report a modified technique of perineal proctectomy using a new reloadable curved cutter stapler, the Contour Transtar (Ethicon Endo-Surgery), to treat full-thickness external rectal prolapse.

METHOD

Between May and July 2008 three female patients were treated. All had a full-thickness external rectal prolapse up to 10 cm in length. The prolapse was initially divided by a linear cutter in anterior and posterior flaps, and resection of the prolapse was performed with a Contour Transtar stapler.

RESULTS

There was no mortality or early or late morbidity. Follow-up was 2-4 months. All patients had a bowel movement within 3 days of the operation, oral feeding started immediately and the hospital stay was 5 days in all cases. All patients reported an improvement of constipation and continence.

CONCLUSION

Our procedure may be indicated for full-thickness prolapse with a rectal protrusion up to 10 cm, as it allows a simple resection without any mobilization or dissection of the rectum. The technique is safe, easier and faster to perform than conventional perineal rectosigmoidectomy.

Controlled deposition of cells in sealed microfluidics using flow velocity boundaries

We present a method for depositing cells in a sealed microfluidic device. The device consists of a poly(dimethylsiloxane) (PDMS) microfluidic network (MFN) sealed with a Si chip. The Si chip has vias and ports that are connected to high-precision motorized pumps. The surfaces of the PDMS MFN are homogeneously coated with fibronectin cell adhesion molecules (CAMs). Flow velocity boundaries are created between vicinal microfluidic structures to prevent or permit deposition of cells in specific regions of the MFN. In narrow flow paths, cells experience a wall shear stress from the fast-moving liquid that overcomes the initial adhesion of the cells with CAMs. Conversely, cells can adhere to CAMs in larger flow paths such as cell chambers inside which the velocity of the liquid and the shear stress are reduced. Interactively changing pumping rates makes the critical velocity (the velocity at which cells deposit in the chamber but not elsewhere) easy to find. The transparent PDMS MFN allows both real-time visualization of the deposition process and cellular assays. We illustrate this method using N9 mouse microglia cells. In one experiment, approximately 75 microglia are deposited per min in a approximately 0.5 microL chamber. The deposited cells remain viable, as assessed from staining and biofunctional assays. This method is simple, reliable, fast, and flexible, and therefore is an attractive technique for depositing cells in microfluidic systems for numerous applications.

The surface-exposed chaperone, Hsp60, is an agonist of the microglial TREM2 receptor

Triggering receptor expressed in myeloid (TREM) cells 2, a receptor expressed by myeloid cells, osteoclasts and microglia, is known to play a protective role in bones and brain. Mutations of the receptor (or of its coupling protein, DAP12) sustain in fact a genetic disease affecting the two organs, the polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy (PLOSL or Nasu-Hakola disease). So far, specific agonist(s) of TREM2 have not been identified and its (their) transduction mechanisms are largely unknown. Heat shock protein 60 (Hsp60) is a mitochondrial chaperone that can also be harboured at the cell surface. By using constructs including the extracellular domain of TREM2 and the Fc domain of IgGs we have identified Hsp60 as the only TREM2-binding protein exposed at the surface of neuroblastoma N2A cells and astrocytes, and lacking in U373 astrocytoma. Treatment with Hsp60 was found to stimulate the best known TREM2-dependent process, phagocytosis, however, only in the microglial N9 cells rich in the receptor. Upon TREM2 down-regulation, the Hsp60-induced stimulation of N9 phagocytosis was greatly attenuated. Hsp60 is also released by many cell types, segregated within exosomes or shedding vesicles which might then undergo dissolution. However, the affinity of its binding (K(d) = 3.8 microM) might be too low for the soluble chaperone released from the vesicles to the extracellular space to induce a significant activation of TREM2. It might in contrast be appropriate for the binding of TREM2 to Hsp60 exposed at the surface of cells closely interacting with microglia. The ensuing stimulation of phagocytosis could play protective effects on the brain.