Impact of mutations at different serine residues on the tyrosine kinase activity of the insulin receptor

Insulin binding to its receptor activates a cascade of signaling events which are initiated by tyrosine autophosphorylation of the receptor and activation of the tyrosine kinase activity towards the insulin receptor substrates. In addition to phosphorylation at tyrosine residues a serine phosphorylation of the insulin receptor is observed. Neither the functional significance of serine phosphorylation of the receptor nor the location of relevant regulatory sites has been determined exactly so far. We studied potential functions of serine residues in human insulin receptor (HIR) with respect to its ability to undergo insulin stimulated autophosphorylation. Using site directed mutagenesis of HIR we exchanged serine to alanine at 13 different positions in the HIR beta-subunit. Sites were chosen according to the criteria of known serine phosphorylation sites (1023/25, 1293/94, 1308/09), conserved positions in hIR, hIGF-1 receptor, hIRR, and dIR (962, 994, 1037, 1055, 1074/78, 1168, 1177/78/82, 1202, 1263, 1267). All HIR mutants were expressed in HEK 293 cells and basal and insulin stimulated autophosphorylation were determined. We found that the exchange of serine to alanine at position 994 and at position 1023/25 increased insulin stimulated receptor autophosphorylation significantly (147% +/- 12% and 129% +/- 6% of control, p < 0.01, n = 7), while all other exchanges did not significantly alter insulin stimulated HIR autophosphorylation. The data suggest that the serine residues at position 994 as well as 1023/25 might be part of inhibitory domains of the insulin receptor.     

Review Paper: Arbuscular Mycorrhiza: Biological, Chemical, and Molecular Aspects

Mycorrhizas are the most important mutualistic symbioses on earth. The most prevalent type are the arbuscular mycorrhizas (AMs) that develop between roots of most terrestrial plants and fungal species of the Zygomycota. The AM fungi are able to grow into the root cortex forming intercellular hyphae from which highly branched structures, arbuscules, originate within cortex cells. The arbuscules are responsible for nutrient exchange between the host and the symbiont, transporting carbohydrates from the plant to the fungus and mineral nutrients, especially phosphate, and water from the fungus to the plant. Plants adapt their phosphate uptake to the interaction with the AM fungus by synthesis of specific phosphate transporters. Colonization of root cells induces dramatic changes in the cytoplasmic organization: vacuole fragmentation, transformation of the plasma membrane to a periarbuscular membrane covering the arbuscule, increase of the cytoplasm volume and numbers of cell organelles, as well as movement of the nucleus into a central position. The plastids form a dense network covering the symbiotic interface. In some of these changes, microtubules are most likely involved. With regard to the molecular crosstalk between the two organisms, a number of phytohormones (cytokinins, abscisic acid, jasmonate) as well as various secondary metabolites have been examined: (i) Jasmonates occur at elevated level, which is accompanied by cell-specific expression of genes involved in jasmonate biosynthesis that might be linked to strong carbohydrate sink function of AM roots and induced defense reactions; (ii) apocarotenoids (derivatives of mycorradicin and glycosylated cyclohexenones) accumulate in most mycorrhizal roots examined so far. Their biosynthesis via the nonmevalonate methylerythritol phosphate (MEP) pathway has been studied resulting in new insights into AM-specific gene expression and biosynthesis of secondary isoprenoids.     

Ohmic contacts for GaAs devices

Contact alloys were developed for use on a wide variety of GaAs devices such as high temperature transistors and Gunn oscillators. The alloys are composed of silver, indium and germanium for n-type GaAs and of silver, indium and zinc for p-type GaAs. Fabrication steps that require temperatures of up to 770°K for already contacted devices can be performed. GaAs transistors can be operated over a range from 20 to 770°K using Ag-In-Ge contacts for emitter and collector and Ag-In-Zn contacts for the base. Gunn oscillators have been built for the frequency range between 13 and 26 GHz with efficiencies as high as 3 percent at 15.8 GHz and as high as 1 percent at 25 GHz in continuous wave operation. A simple technique was developed to evaluate the specific contact resistance on thin epitaxial layers. Specific contact resistance is well below 10⁻⁴ ω-cm² on 0.1 ω-cm or lower resistivity p- or n-type GaAs. The highest value was 1 × 10⁻³ ω-cm² measured on 0.6–2.6 ω-cm n-type GaAs.     

The detrimental influence of stacking faults on the refresh time of MOS memories

The reverse current of diodes and the storage capability of MOS capacitors were investigated and the detrimental influence of stacking faults in the respective active area is demonstrated. In the case of the relaxation time of MOS capacitors it is shown that their deterioration can be related to the number of the stacking faults in the MOS capacitors resulting in a deterioration of the refresh behaviour of dynamic memories. The influence of one single stacking fault on the dynamic behaviour of a MOS capacitor is demonstrated. From transmission electron microscopy (TEM) and neutron activation analysis it is concluded that stacking faults decorated by Cu or Fe are most harmful to the refresh behaviour.     

Validating Theories for Brittle Damage

Validating simulated predictions of internal damage within armor ceramics is preferable to simply assessing a model’s ability to predict penetration depth, especially if one hopes to perform subsequent “second strike” analyses. We present the results of a study in which crack networks are seeded by using a statistically perturbed strength, the median of which is inherited from a deterministic “smeared damage” model, with adjustments to reflect experimentally established size effects. This minor alteration of an otherwise conventional damage model noticeably mitigates mesh dependencies and, at virtually no computational cost, produces far more realistic cracking patterns that are well suited for validation against X-ray computed tomography (XCT) images of internal damage patterns. For Brazilian, spall, and indentation tests, simulations share qualitative features with externally visible damage. However, the need for more stringent quantitative validation, software quality testing, and subsurface XCT validation, is emphasized.     

Attractiveness of the underling: An automatic power?→?sex association and its consequences for sexual harassment and aggression.

One characteristic of men who sexually harass is that they are not aware that their actions are inappropriate or a misuse of their power (L. F Fitzgerald, 1993a). We investigated the existence and automaticity of a mental association between the concepts of power and sex, and its consequences for sexual harassment tendencies. Using a subliminal priming paradigm, Experiment 1 demonstrated an automatic link between power and sex, and only for men high in the likelihood to sexually harass or aggress. In Experiment 2, male participants were unobtrusively primed with either power related or neutral stimuli. For men likely to sexually aggress, but not other participants, attraction ratings of a female confederate were significantly higher in the power priming than the neutral priming condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Explaining the enigmatic anchoring effect: Mechanisms of selective accessibility.

Results of 3 studies support the notion that anchoring is a special case of semantic priming; specifically, information that is activated to solve a comparative anchoring task will subsequently be more accessible when participants make absolute judgments. By using the logic of priming research, in Study 1 the authors showed that the strength of the anchor effect depends on the applicability of activated information. Study 2 revealed a contrast effect when the activated information was not representative for the absolute judgment and the targets of the 2 judgment tasks were sufficiently different. Study 3 demonstrated that generating absolute judgments requires more time when comparative judgments include an implausible anchor and can therefore be made without relevant target information that would otherwise be accessible. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperthyroidism induced by iodinated roentgen contrast media]

Three patients with subclinical hyperthyroid goitre, women aged 63, 72 and 75 years following intravenous administration of an iodinated contrast medium developed hyperthyroidism with a marked rise of the concentration of free T4. Thyreostatic agents were unsuccessful in two patients, the third was left untreated. Hyperthyroidism improved spontaneously in all three. Iodine-induced hyperthyroidism is rare and is usually encountered in patients with a pre-existent autonomous thyroid function. Treatment of iodine-induced hyperthyroidism is essentially exclusively symptomatic. Prophylaxis with sodium perchlorate should be considered in cardiac patients with a goitre and a subnormal level of thyroid-stimulating hormone (TSH).