MICU1 Controls Both the Threshold and Cooperative Activation of the Mitochondrial Ca2+ Uniporter

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Calibration and uncertainties in personal exposure measurements of radiofrequency electromagnetic fields

In the past 5 years radiofrequency personal exposure meters have been used to characterize the exposure during daily activities. We found from calibration tests for the 12 frequency bands of the EME Spy 121 exposimeter in a Gigahertz Transverse Electromagnetic cell and an Open Area Test Site, that these measurements tend to underestimate the actual exposure. Therefore, a maximum frequency‐dependent correction factor of 1.1–1.6 should be applied to the electric field. This correction factor consists of three multipliers correcting for calibration, elevation arrival angle, and influence of the body. The calibration correction factor should be determined per exposimeter, as the maximum range of response between exposimeters in a frequency band is 2.4 dB. Since the range of response for different elevation angles could reach 10.2 dB, a strict protocol for wearing the exposimeter during fieldwork should be followed to be able to compare and combine measurements made by different persons in the same microenvironments. Because the influence of the body depends on the azimuth angle of arrival, it may lead to an over‐ or underestimation. Thus, the body correction factor is an average over the angles and should only be applied in activities involving movement through the full 360° range of random angles of arrival. Bioelectromagnetics. Bioelectromagnetics 32:652–663, 2011. © 2011 Wiley Periodicals, Inc.     

Origin of the stability conferred upon collagen by fluorination

According to a prevailing theory, (2S,4R)-4-hydroxyproline (Hyp) residues stabilize the collagen triple helix via a stereoelectronic effect that preorganizes appropriate backbone torsion angles for triple-helix formation. This theory is consistent with the marked stability that results from replacing the hydroxyl group with the more electron-withdrawing fluoro group, as in (2S,4R)-4-fluoroproline (Flp). Nonetheless, the hyperstability of triple helices containing Flp has been attributed by others to the hydrophobic effect rather than a stereoelectronic effect. We tested this hypothesis by replacing Hyp with 4,4-difluoroproline (Dfp) in collagen-related peptides. Dfp retains the hydrophobicity of Flp, but lacks the ability of Flp to preorganize backbone torsion angles. Unlike Flp, Dfp does not endow triple helices with elevated stability, indicating that the hyperstability conferred by Flp is not due to the hydrophobic effect.     

Proapoptotic BID is an ATM effector in the DNA-damage response

The "BH3-only" proapoptotic BCL-2 family members are sentinels of intracellular damage. Here, we demonstrated that the BH3-only BID protein partially localizes to the nucleus in healthy cells, is important for apoptosis induced by DNA damage, and is phosphorylated following induction of double-strand breaks in DNA. We also found that BID phosphorylation is mediated by the ATM kinase and occurs in mouse BID on two ATM consensus sites. Interestingly, BID-/- cells failed to accumulate in the S phase of the cell cycle following treatment with the topoisomerase II poison etoposide; reintroducing wild-type BID restored accumulation. In contrast, introducing a nonphosphorylatable BID mutant did not restore accumulation in the S phase and resulted in an increase in cellular sensitivity to etoposide-induced apoptosis. These results implicate BID as an ATM effector and raise the possibility that proapoptotic BID may also play a prosurvival role important for S phase arrest.     

On the histochemical differences of aldehyd-fuchsin positive material in the fibres of the hypothalamo-hypophyseal tract of Rana temporaria

Summary Using a modified Alcian blue/Alcian yellow method, differences in stainability in the fibres of the preoptic-hypophyseal tract of Rana temporaria were observed. Near the preoptic nucleus most of the fibres stained yellow, in the tract the fibres stained lightgreen or showed green inclusions on a yellow background, whereas at the fibre-endings a colour switch to blue-green was found. This colour switch was the most pronounced in the neural lobe, where the neurosecretion stained blue-green, whereas in the fibre-endings in the outer zone of the median eminence a colour switch to green was noticed.The results can best be explained with the assumption that a modification or transformation of the neurosecretion occurs during its transport from the preoptic nucleus to the fibre-endings.Literature related to this hypothesis is discussed.     

Effects of magnesium sulphate following spinal cord injury in rats

Neutrophil infiltration has been implicated in the secondary destructive pathomechanisms after initial mechanical injury to the spinal cord. Tissue myeloperoxidase (MPO) activity has been shown to be an exclusive indicator of the extent of post-traumatic neutrophil infiltration. We have studied the effect of magnesium sulphate on MPO activity after spinal cord injury in rats. Rats were randomly allocated into 5 groups. Group 1 was control and normal spinal cord samples were obtained after clinical examination. Forty g-cm contusion injury was introduced to Group 2. Group 3 was vehicle, 1 ml of physiological saline was injected post-trauma. Group 4 was given 30 mg/kg methylprednisolone sodium succinate (MPSS) immediately after trauma. Group 5 was given 600 mg/kg magnesium sulphate immediately after trauma. Animals were examined by inclined plane technique of Rivlin and Tator 24 h after trauma. Spinal cord samples obtained following clinical evaluations. Magnesium sulphate treatment improved early functional scores and decreased MPO activity. These findings revealed that magnesium sulphate treatment possesses neuroprotection on early clinical results and on neutrophil infiltration after acute contusion injury to the rat spinal cord.     

A conserved interaction with the chromophore of fluorescent proteins

The chromophore of fluorescent proteins, including the green fluorescent protein (GFP), contains a highly conjugated imidazolidinone ring. In many fluorescent proteins, the carbonyl group of the imidazolidinone ring engages in a hydrogen bond with the side chain of an arginine residue. Prior studies have indicated that such an electrophilic carbonyl group in a protein often accepts electron density from a main-chain oxygen. A survey of high-resolution structures of fluorescent proteins indicates that electron lone pairs of a main-chain oxygen-Thr62 in GFP-donate electron density into an antibonding orbital of the imidazolidinone carbonyl group. This n→π* electron delocalization prevents structural distortion during chromophore excitation that could otherwise lead to fluorescence quenching. In addition, this interaction is present in on-pathway intermediates leading to the chromophore, and thus could direct its biogenesis. Accordingly, this n→π* interaction merits inclusion in computational and photophysical analyses of the chromophore, and in speculations about the molecular evolution of fluorescent proteins.     

A fluorescent modification of the Sakaguchi reaction on arginine

Summary The reactionproduct of arginine with 2,4-dichloro--naphthol proved to be fluorescent. This fluorescence could be used for the histochemical localization of arginine. The modification described resulted in a long lasting yellow-orange fluorescence of various arginine-containing tissues.Thanks are due to Mr. H. van Kooten for making the photograph.     

Extracellular enzyme activity: Indications for high short-term variability in a coastal marine ecosystem

Extracellular -glucosidase, -glucosidase, and aminopeptidase activity variations (measured by use of fluorogenic substrate analogs) at a coastal station in the Mediterranean Sea were investigated over a 1-year period. A 27-h cycle and daily measurements were made in a summer situation. We observed strong relative diurnal variations, compared to seasonal variations, in - and -glucosidase. Within 24 h, 0–100% of both - and -glucosidase were found in the dissolved phase. The aminopeptidase activities did not show a strong diurnal variation, but day to day variations were similar in magnitude to seasonal changes. Consistently, high proportions of all three enzymes were found in the dissolved phase on a seasonal scale. Seasonal measurements at 50- and 100-m depths showed a weak negative dependency on depth for extracellular enzyme activity. The potential importance of both hourly and daily changes in extracellular enzyme activity and of free enzymes is considered. Correspondence to: M. Karner