Spin splitting of X-related donor impurity states in an AlAs barrier

We use magnetotunneling spectroscopy to observe the spin splitting of the ground state of an X-valley-related Si-donor impurity in an AlAs barrier. We determine the absolute magnitude of the effective Zeeman spin splitting factors of the impurity ground state to be g$_{I}$= 2.2 $\pm$ 0.1. We also investigate the spatial form of the electron wave function of the donor ground state, which is anisotropic in the growth plane

Chapter 5-Parkinson's disease - A role of non-enzymatic posttranslational modifications in disease onset and progression?

Parkinson's disease (PD) is a still incurable neurodegenerative disorder with a highly complex etiology. While about 10% of cases are associated with single-gene mutations, the majority of PD is thought to originate from a combination of factors such as environmental impact, lifestyle and aging. Even though investigations into the genetically caused cases have uncovered major pathomechanisms of the disease there still exists a wide gap concerning the molecular impact of the other risk factors. All of them are known to have a major impact on the oxidative burden of the cell and thus strongly influence the non-enzymatic posttranslational modifications (nePTMs) of proteins. These modifications are by now known to dramatically alter the stability of proteins, their interactomes, and also their functions. However, the knowledge of nePTMs and their possible causative role in the pathoetiology of PD is just starting to emerge again guided by research on PD-associated genes. In this short review, we will thus concentrate on known nePTMs of two PD-associated genes, SCNA and DJ-1, and discuss their role in the pathoetiology of PD. In the future, it will, however, be essential to unravel the complete environmental proteome to understand the impact of nePTMs on PD etiology. This might open up new pathways urgently needed to develop new diagnostic and therapeutic tools for this still incurable disease

Gene Expression Profiling Following Maternal Deprivation: Involvement of the Brain Renin-Angiotensin System

The postnatal development of the mouse is characterized by a stress hypo-responsive period (SHRP), where basal corticosterone levels are low and responsiveness to mild stressors is reduced. Maternal separation is able to disrupt the SHRP and is widely used to model early trauma. In this study we aimed at identifying of brain systems involved in acute and possible long-term effects of maternal separation. We conducted a microarray-based gene expression analysis in the hypothalamic paraventricular nucleus after maternal separation, which revealed 52 differentially regulated genes compared to undisturbed controls, among them are 37 up-regulated and 15 down-regulated genes. One of the prominently up-regulated genes, angiotensinogen, was validated using in-situ hybridization. Angiotensinogen is the precursor of angiotensin II, the main effector of the brain renin-angiotensin system (RAS), which is known to be involved in stress system modulation in adult animals. Using the selective angiotensin type I receptor [AT(1)] antagonist candesartan we found strong effects on CRH and GR mRNA expression in the brain and ACTH release following maternal separation. AT(1) receptor blockade appears to enhance central effects of maternal separation in the neonate, suggesting a suppressing function of brain RAS during the SHRP. Taken together, our results illustrate the molecular adaptations that occur in the paraventricular nucleus following maternal separation and contribute to identifying signaling cascades that control stress system activity in the neonate

Expression of a catalytically inactive mutant form of glutathione peroxidase 4 (Gpx4) confers a dominant-negative effect in male fertility.

The selenoenzyme Gpx4 is essential for early embryogenesis and cell viability for its unique function to prevent phospholipid oxidation. Recently, the cytosolic form of Gpx4 was identified as an upstream regulator of a novel form of non-apoptotic cell death, called ferroptosis, whereas the mitochondrial isoform of Gpx4 (mGpx4) was previously shown to be crucial for male fertility. Here, we generated and analyzed mice with targeted mutation of the active site selenocysteine (Sec) of Gpx4 (Gpx4_U46S). Mice homozygous for Gpx4_U46S died at the same embryonic stage (E7.5) as Gpx4-/- embryos as expected. Surprisingly, male mice heterozygous for Gpx4_U46S presented subfertility. Subfertility was manifested in a reduced number of litters from heterozygous breedings and an impairment of spermatozoa to fertilize oocytes in vitro. Morphologically, sperm isolated from heterozygous Gpx4_U46S mice revealed many structural abnormalities particularly in the spermatozoan midpiece due to improper oxidation and polymerization of sperm capsular proteins and malformation of the mitochondrial capsule surrounding and stabilizing sperm mitochondria. These findings are reminiscent of sperm isolated from selenium-deprived rodents or from mice specifically lacking mGpx4. Due to a strongly facilitated incorporation of Ser in the polypeptide chain as compared to Sec at the UGA codon, expression of the catalytically inactive Gpx4_U46S was found to be strongly increased. Since the stability of the mitochondrial capsule of mature spermatozoa depends on the moonlighting function of Gpx4 both as an enzyme oxidizing capsular protein thiols and being a structural protein, tightly controlled expression of functional Gpx4 emerges being key for full male fertility

Acidification increases microbial polysaccharide degradation in the ocean

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 1615–1624, doi:10.5194/bg-7-1615-2010.With the accumulation of anthropogenic carbon dioxide (CO2), a proceeding decline in seawater pH has been induced that is referred to as ocean acidification. The ocean's capacity for CO2 storage is strongly affected by biological processes, whose feedback potential is difficult to evaluate. The main source of CO2 in the ocean is the decomposition and subsequent respiration of organic molecules by heterotrophic bacteria. However, very little is known about potential effects of ocean acidification on bacterial degradation activity. This study reveals that the degradation of polysaccharides, a major component of marine organic matter, by bacterial extracellular enzymes was significantly accelerated during experimental simulation of ocean acidification. Results were obtained from pH perturbation experiments, where rates of extracellular α- and β-glucosidase were measured and the loss of neutral and acidic sugars from phytoplankton-derived polysaccharides was determined. Our study suggests that a faster bacterial turnover of polysaccharides at lowered ocean pH has the potential to reduce carbon export and to enhance the respiratory CO2 production in the future ocean.This study was supported by the Helmholtz Association (HZ-NG-102) and the Belgian Science Policy (SD/CS/03)

MULTIPLE CEREBRAL METASTASES MIMICKING WERNICKE'S ENCEPHALOPATHY IN A CHRONIC ALCOHOLIC

Aims: Alcohol dependent patients in withdrawal display a wide spectrum of neurological and neuropsychological symptoms that complicate diagnosis. We report the case of a 53-year-old male alcoholic with disorientation, ataxia and nystagmus in alcohol withdrawal probably due not to initial supposed Wernicke's encephalopathy (WE) but rather due to multiple cerebral metastases of a non-small cell cancer of the lung. Results: The findings illustrate the importance of initially maintaining a tentative attitude toward causation of symptoms and the role of brain imaging in formulating an accurate diagnosi

Letter to the EditorA clinical lesson: Glioblastoma multiforme masquerading as depression in a chronic alcoholic

Aims: To highlight the need to consider other medical conditions when the presentation initially appears to be alcohol-related. Method: We report the case of a 34-year-old male alcoholic, who presented with clinical depression and later a delirious state, and was subsequently diagnosed to have a right frontal glioblastoma multiforme. Conclusions: Psychiatric patients, especially alcoholics, may present with physical and neurological symptoms in the emergency department, which are linked by the examiner to the toxic effects of alcohol. However, consideration should be given to the possibility that the symptoms are due to other severe medical condition

Magnetic-field-induced singularities in spin dependent tunneling through InAs quantum dots

Current steps attributed to resonant tunneling through individual InAs quantum dots embedded in a GaAs-AlAs-GaAs tunneling device are investigated experimentally in magnetic fields up to 28 T. The steps evolve into strongly enhanced current peaks in high fields. This can be understood as a field-induced Fermi-edge singularity due to the Coulomb interaction between the tunneling electron on the quantum dot and the partly spin polarized Fermi sea in the Landau quantized three-dimensional emitter.Comment: 5 pages, 4 figure