Altered synaptobrevin-II trafficking in neurons expressing a synaptophysin mutation associated with a severe neurodevelopmental disorder

textabstractFollowing exocytosis, synaptic vesicles (SVs) have to be reformed with the correct complement of proteins in the correct stoichiometry to ensure continued neurotransmission. Synaptophysin is a highly abundant, integral SV protein necessary for the efficient retrieval of the SV SNARE protein, synaptobrevin II (sybII). However the molecular mechanism underpinning synaptophysin-dependent sybII retrieval is still unclear. We recently identified a male patient with severe intellectual disability, hypotonia, epilepsy and callosal agenesis who has a point mutation in the juxtamembrane region of the fourth transmembrane domain of synaptophysin (T198I). This mutation had no effect on the activity-dependent retrieval of synaptophysin that was tagged with the genetically-encoded pH-sensitive reporter (pHluorin) in synaptophysin knockout hippocampal cultures. This suggested the mutant has no global effect on SV endocytosis, which was confirmed when retrieval of a different SV cargo (the glutamate transporter vGLUT1) was examined. However neurons expressing this T198I mutant did display impaired activity-dependent sybII retrieval, similar to that observed in synaptophysin knockout neurons. Interestingly this impairment did not result in an increased stranding of sybII at the plasma membrane. Screening of known human synaptophysin mutations revealed a similar presynaptic phenotype between T198I and a mutation found in X-linked intellectual disability. Thus this novel human synaptophysin mutation has revealed that aberrant retrieval and increased plasma membrane localisation of SV cargo can be decoupled in human disease

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

A fine balance of synaptophysin levels underlies efficient retrieval of synaptobrevin II to synaptic vesicles

Synaptobrevin II (sybII) is a vesicular soluble NSF attachment protein receptor (SNARE) protein that is essential for neurotransmitter release, and thus its correct trafficking to synaptic vesicles (SVs) is critical to render them fusion competent. The SV protein synaptophysin binds to sybII and facilitates its retrieval to SVs during endocytosis. Synaptophysin and sybII are the two most abundant proteins on SVs, being present in a 1:2 ratio. Synaptophysin and sybII are proposed to form a large multimeric complex, and the copy number of the proteins in this complex is also in a 1:2 ratio. We investigated the importance of this ratio between these proteins for the localisation and trafficking of sybII in central neurons. SybII was overexpressed in mouse hippocampal neurons at either 1.6 or 2.15-2.35-fold over endogenous protein levels, in the absence or presence of varying levels of synaptophysin. In the absence of exogenous synaptophysin, exogenous sybII was dispersed along the axon, trapped on the plasma membrane and retrieved slowly during endocytosis. Co-expression of exogenous synaptophysin rescued all of these defects. Importantly, the expression of synaptophysin at nerve terminals in a 1:2 ratio with sybII was sufficient to fully rescue normal sybII trafficking. These results demonstrate that the balance between synaptophysin and sybII levels is critical for the correct targeting of sybII to SVs and suggests that small alterations in synaptophysin levels might affect the localisation of sybII and subsequent presynaptic performance

Ein Extremal-Variationsprinzip fuer die instationaere Waermeleitung mit einer Anwendung auf thermoelastische Probleme unter Verwendung der finiten Elemente

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Permissive tolerance of the patent ductus arteriosus may increase the risk of Chronic Lung Disease

Joseph W Kaempf,1 Robert Huston,2 YingXing Wu,1 Andrew J Kaempf,1 Lian Wang,1 Gary Grunkemeier,1 Rebecca Mischel,2 Howard Cohen,3 Bret Freitag41Providence St Vincent Medical Center, Portland, OR, 2Randall Children’s Hospital at Legacy Emanuel, Portland, OR, 3Salem Hospital, Salem, OR, 4Legacy Salmon Creek Hospital, Vancouver, WA, USAPurpose: Because early closure therapies of the patent ductus arteriosus (PDA) have not been shown to confer benefit to premature infants, the authors’ four neonatal intensive care units adopted a less aggressive PDA management protocol.Study design: A before–after investigation in infants with PDAs born 501–1500 g. Era 1 (January 2005 to December 2007) featured traditional management with indomethacin and/or surgical ligation used early to close PDAs; Era 2 (January 2008 to June 2009) featured fluid restriction and watchful waiting for PDA closure, limiting indomethacin or surgical ligation to only those infants with large PDAs needing significant respiratory support.Results: Era 2 infants (n = 129, mean ± standard deviation 27 ± 2 weeks) received less and later indomethacin and less Day 1–28 total fluids as compared to Era 1 infants (n = 240, mean ± standard deviation 27 ± 2 weeks). The Chronic Lung Disease (CLD) rate was higher in Era 2 (48% versus 34%, P < 0.01) as was the combined outcome of Death after Day 7 or CLD (57% versus 42%, P < 0.01). Multiple regression analysis showed Era 2 birth was a predictor of CLD. However, Poisson regression analysis determined the predictors of all seven major Vermont Oxford Network morbidities were earlier gestational age, lower birth weight, and male gender, not the era of birth. Significantly more infants were discharged home with PDAs in Era 2.Conclusion: Permissive tolerance of PDAs may increase the risk of CLD and Death after Day 7 or CLD but is not associated with significant changes in other Vermont Oxford Network morbidities.Keywords: premature infant, indomethacin, surgical ligation, quality improvemen