Crosstalk in the retinal neurovascular unit - lessons for the diabetic retina

Diabetic retinopathy shares important features with neurodegenerative retinal diseases, including loss of ganglion cells and retinal thinning. The impact on vasoregression and subsequent ischemia-driven changes such as macular edema and proliferative retinopathy are not established. Studies using adult neurodegenerative animal models such as the transgenic TGR(CMV-PKD2(1/703)HA) rat imply early activation of the innate immunity system and the complement system as well as microglia playing a role in the damage of the retinal neurovascular unit.

Fitting in a complex χ(2) landscape using an optimized hypersurface sampling

Fitting a data set with a parametrized model can be seen geometrically as finding the global minimum of the χ(2) hypersurface, depending on a set of parameters {P(i)}. This is usually done using the Levenberg-Marquardt algorithm. The main drawback of this algorithm is that despite its fast convergence, it can get stuck if the parameters are not initialized close to the final solution. We propose a modification of the Metropolis algorithm introducing a parameter step tuning that optimizes the sampling of parameter space. The ability of the parameter tuning algorithm together with simulated annealing to find the global χ(2) hypersurface minimum, jumping across χ(2){P(i)} barriers when necessary, is demonstrated with synthetic functions and with real data.

Abstract P4-05-05: Stromal Response to 14-Day Preoperative Therapy in Postmenopausal Oestrogen Receptor Positive Breast Cancer

Background: Stromal-epithelial interaction is a key factor in tumour progression. Cancer-associated fibroblasts (CAFs) and macrophage infiltration have been associated with early relapse in breast cancer. Bisphosphonates are effective inhibitors of osteoclast activation in metastatic breast cancer but also have a general inhibitory effect on breast cancer progression. In order to monitor a potential tumour stromal response in breast cancer during treatment with an aromatase inhibitor and a bisphosphonate we analysed pre-and post-treatment samples from a neoadjuvant window study and focused on the presence of macrophages and CAFs.

Materials and methods: Tissue microarrays (TMAs) from surgical samples and pre-operative core biopsies were immunohistochemically stained for aSMA (CAF marker), CD68 (macrophages) and epithelial proliferation (Ki67). In order to validate if the presence of macrophages and aSMA could be monitored by the TMA approach, we initially analysed a screening cohort of 144 breast cancer samples. We then studied pre-and post-treatment samples from 110 postmenopausal ER-positive invasive breast cancer patients randomised to receive 14 days of preoperative treatment (placebo, Letrozole, or Letrozole plus Zoledronate). Results: In the screening cohort, we observed significant links between aSMA positive fibroblasts and disease recurrence as well as between CD68 positive macrophages and tumour size, grade, lymph node positivity and recurrence. This validated the use of TMAs for stromal analyses and furthersupported a link with key tumour biological events. In both treatment arms, there was a significant drop in absolute Ki67 value compared to placebo (-9.3% Letrozole and -13.1% combination reduction versus 1% increase, P<0.001). Post-treatment CD68 (median 35, range 3 to 117) was significantly linked to a Ki67 drop (p=0.045). Interestingly, this effect was mainly observed in the combination treatment group (p=0.002). aSMA expression was unaffected during treatment in 52%, increased in 35% and decreased in 13% of cases. Patients with aSMA reduction post treatment had a larger Ki67 fall compared to patients with increase or no change in aSMA (p=0.007).

Conclusion: Short term treatment response in the epithelial component of cancers was paralleled by specific responses in the tumour stromal component. These novel findings suggest that bisphosphonates and aromatase inhibitors have major effects on tumour stroma in vivo which might augment their inhibitory effect on tumour progression.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-05-05.

Abstract P2-09-34: ERK Phosphorylation in Fibroblasts within Breast Cancer Stroma Is Associated with an Improved Tamoxifen Response

Background. Extra-cellular signal-regulated kinase (ERK) 1/2 is an integral part of the mitogen-activated protein kinase (MAPK) pathway, transmitting signals involved in cell proliferation and cell death upon binding of extracellular growth factors to their receptors. Whereas its role in tumour cells has been linked to key events in cell transformation, its role in tumour-associated fibroblasts, a component of the tumour stroma, is largely unknown.

Material and methods. Tissue microarrays (TMAs) of two cohorts including invasive breast cancer patients were stained for ERK phosphorylation level (pERK) and SMA-alpha expression (SMAa) which were scored and analysed in regard to clinico-pathological, prognostic and molecular markers and recurrence-free survival.

Results. In both clinical materials we show a significant correlation between stromal ERK phosphorylation and the marker for activated fibroblasts SMAa. SMAa expression was not linked to treatment-predictive information but instead had prognostic qualities (P=0.034, multivariate Cox regression). By analysing the unique randomised tamoxifen trial including patients receiving no adjuvant treatment we show for the first time that ERK phosphorylation in cancer-associated fibroblasts (CAF) was associated with an improved outcome upon tamoxifen treatment. In contrast, patients having ERα-positive tumours but lacking ERK phosphorylation in the stroma did not respond to tamoxifen treatment (P=0.015, multivariate interaction analyses).

Discussion. This suggests that only a subpopulation of activated fibroblasts, defined by phosphorylation of ERK, is linked to a response to tamoxifen treatment illustrating the importance of the stroma for monitoring and potentially mediating treatment effects in premenopausal breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-34.

Dynamical transition of protein-hydration water

Thin layers of water on biomolecular and other nanostructured surfaces can be supercooled to temperatures not accessible with bulk water. Chen et al. [Proc. Natl. Acad. Sci. U.S.A. 103, 9012 (2006)]10.1073/pnas.0602474103 suggested that anomalies near 220 K observed by quasielastic neutron scattering can be explained by a hidden critical point of bulk water. Based on more sensitive measurements of water on perdeuterated phycocyanin, using the new neutron backscattering spectrometer SPHERES, and an improved data analysis, we present results that show no sign of such a fragile-to-strong transition. The inflection of the elastic intensity at 220 K has a dynamic origin that is compatible with a calorimetric glass transition at 170 K. The temperature dependence of the relaxation times is highly sensitive to data evaluation; it can be brought into perfect agreement with the results of other techniques, without any anomaly.

Health‐Related Quality of Life in Children and Adolescents with Asthma: Results from the ESTAR Study

Our aim was to assess the psychosocial well-being of asthmatic children and adolescents, the influencing factors, and to determine the effect of inpatient rehabilitation on their quality of life; 226 asthmatic children and adolescents participated in the inpatient rehabilitation (IG). The comparison group (CG) included 92 asthmatic children and adolescents receiving standard medical treatments. Patients were aged between 8 and 16 years and were predominantly male. The health-related quality of life was measured with the German version of the "Paediatric Asthma Quality of Life Questionnaire." Interviews were carried out for IG 2 weeks before the commencement of their inpatient stay and 1 year after their stay ended. The same time schedule was carried out for CG. All patients reported a mild to moderate impairment of their quality of life. Girls described a slightly lower quality of life than boys. With increasing asthma severity, quality of life decreased. Inpatients described a lower quality of life than CG at enrollment. Inpatient rehabilitation resulted in a greater improvement of quality of life over time for IG than for CG. Gender and severity status had no effect on this time course. The only modestly affected quality of life may reflect the good adaptation to the disease and medical treatment. Children and adolescents in the IG recorded improvements in their quality of life. Differences in quality of life based on gender and disease severity were not shown to influence the improvements. In summary, inpatient rehabilitation results in an improvement of health-related quality of life. Further research concerning the psychosocial situation of children and adolescents in this setting is needed.

Dynamics in shear flow studied by X-ray Photon Correlation Spectroscopy

X-ray Photon Correlation Spectroscopy was used to measure the diffusive dynamics of colloidal particles in a shear flow. The results presented here show how the intensity autocorrelation functions measure both the diffusive dynamics of the particles and their flow-induced, convective motion. However, in the limit of low flow/shear rates, it is possible to obtain the diffusive component of the dynamics, which makes the method suitable for the study of the dynamical properties of a large class of complex soft-matter and biological fluids. An important benefit of this experimental strategy over more traditional X-ray methods is the minimization of X-ray-induced beam damage. While the method can be applied also for photon correlation spectroscopy in the visible domain, our analysis shows that the experimental conditions under which it is possible to measure the diffusive dynamics are easier to achieve at higher q values (with X-rays).

Dynamics of well-folded and natively disordered proteins in solution: a time-of-flight neutron scattering study

Casein proteins belong to the class of natively disordered proteins. The existence of disordered biologically active proteins questions the assumption that a well-folded structure is required for function. A hypothesis generally put forward is that the unstructured nature of these proteins results from the functional need of a higher flexibility. This interplay between structure and dynamics was investigated in a series of time-of-flight neutron scattering experiments, performed on casein proteins, as well as on three well-folded proteins with distinct secondary structures, namely, myoglobin (alpha), lysozyme (alpha/beta) and concanavalin A (beta). To illustrate the subtraction of the solvent contribution from the scattering spectra, we used the dynamic susceptibility spectra emphasizing the high frequency part of the spectrum, where the solvent dominates. The quality of the procedure is checked by comparing the corrected spectra to those of the dry and hydrated protein with negligible solvent contamination. Results of spectra analysis reveal differences in motional amplitudes of well-folded proteins, where beta-sheet structures appear to be more rigid than a cluster of alpha-helices. The disordered caseins display the largest conformational displacements. Moreover their global diffusion rates deviate from the expected dependence, suggesting further large-scale conformational motions.

Contrast enhanced ultrasound and Dual Source CT of left atrial myxoma

PURPOSE

Myxomas of the left atrial cavity of the heart are a rare occurrence. Incidental diagnosis is mostly based on transthoracic echocardiography. Contrast enhanced ultrasound (CEUS) seems to be a promising new diagnostic option for diagnosis and preoperative planning of treatment for patients with myxoma. It is an additional examination to baseline ultrasound and CT or MRT.

MATERIALS AND METHODS

We report a case of a 63-year-old woman with myxoma of the left atrial cavity of the heart in which CEUS helped to define the location and its relation to the heart valve.

RESULTS

In contrast enhanced ultrasound (CEUS), the oval mass in the left atrium was scanned in the 4-chamber view. Perfusion of the mass was examined by visualising gradual contrast enhancement. An involvement of the mitral valve could be excluded. The tumour base could be clearly depicted and differentiated from normal surrounding tissue. No thrombotic material was found in the left atrium (LA) or ventricle (LV).

CONCLUSION

CEUS could detect the mass and offer additional information such as vascularity, mobility, attachment to the valve and possible thrombi. Dual Source CT (DSCT) confirmed the findings and provided a very clear morphological characterisation and dynamic evaluation of mobility and valve interference.

Quantitative assessment of left ventricular function with dual-source CT in comparison to cardiac magnetic resonance imaging: initial findings

Cardiac magnetic resonance imaging and echocardiography are currently regarded as standard modalities for the quantification of left ventricular volumes and ejection fraction. With the recent introduction of dual-source computedtomography (DSCT), the increased temporal resolution of 83 ms should also improve the assessment of cardiac function in CT. The aim of this study was to evaluate the accuracy of DSCT in the assessment of left ventricular functional parameters with cardiac magnetic resonance imaging (MRI) as standard of reference. Fifteen patients (two female, 13 male; mean age 50.8 +/- 19.2 years) underwent CT and MRI examinations on a DSCT (Somatom Definition; Siemens Medical Solutions, Forchheim, Germany) and a 3.0-Tesla MR scanner (Magnetom Trio; Siemens Medical Solutions), respectively. Multiphase axial CT images were analysed with a semiautomatic region growing algorithms (Syngo Circulation; Siemens Medical Solutions) by two independent blinded observers. In MRI, dynamic cine loops of short axis slices were evaluated with semiautomatic contour detection software (ARGUS; Siemens Medical Solutions) independently by two readers. End-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction (EF) and stroke volume (SV) were determined for both modalities, and correlation coefficient, systematic error, limits of agreement and inter-observer variability were assessed. In DSCT, EDV and ESV were 135.8 +/- 41.9 ml and 54.9 +/- 29.6 ml, respectively, compared with 132.1 +/- 40.8 ml EDV and 57.6 +/- 27.3 ml ESV in MRI. Thus, EDV was overestimated by 3.7 ml (limits of agreement -46.1/+53.6), while ESV was underestimated by 2.6 ml (-36.6/+31.4). Mean EF was 61.6 +/- 12.4% in DSCT and 57.9 +/- 9.0% in MRI, resulting in an overestimation of EF by 3.8% with limits of agreement at -14.7 and +22.2%. Rank correlation rho values were 0.81 for EDV (P = 0.0024), 0.79 for ESV (P = 0.0031) and 0.64 for EF (P = 0.0168). The kappa value of inter-observer variability were amounted to 0.85 for EDV, ESV and EF. DSCT offers the possibility to quantify left ventricular function from coronary CT angiography datasets with sufficient diagnostic accuracy, adding to the value of the modality in a comprehensive cardiac assessment. The observed differences in the measured values may be due to different post-processing methods and physiological reactions to contrast material injection without beta-blocker medication.

Dual-source-Computertomographie des Herzens

In a newly developed dual-source computed tomography system (DSCT) the relation of heart rate and image quality and the possible advantages of the system's superior temporal resolution in the evaluation of left ventricular parameters as compared to results of cardiac magnetic resonance imaging (MRI) were assessed. Coronary CT angiography was performed using a DSCT (Somatom Defintion, Siemens Medical Solutions, Forchheim, Germany) in 21 patients (mean age 62+/-8; 15 male, 6 female). Image quality of the coronary arteries, the heart valves, and the left ventricular myocardium was assessed using a three-point grading scale. Ten of these patients also underwent cardiac MRI for the assessment of left ventricular function, using a SSFP (steady-state free precession) sequence. Left ventricular ejection fractions (LV-EF), the end-systolic volumes (ESV), and the end-diastolic volumes (EDV) were measured employing MRI and DSCT datasets. The image quality ratings for the coronary arteries at the optimal reconstruction interval were diagnostic even in patients with high heart rates (1.42+/-0.49). Analysis of global LV function using DSCT quantified from CTA datasets showed a good correlation with results of cardiac MRI [EF: r=0.75 (p=0.01); ESV: r=0.72 (p=0.19); EDV: r=0.71 (p=0.02)]. The dual-source CT system offers robust image quality of the coronary arteries, independent of the heart rate, and provides combined diagnostic imaging of coronary arteries, the heart valves, the myocardium, and the global left ventricular function.

Combined targeting of MAPK and AKT signalling pathways is a promising strategy for melanoma treatment

BACKGROUND

In melanoma, several signalling pathways are constitutively activated. Among them, the RAS/RAF/MEK/ERK (MAPK) and PI3K/AKT (AKT) signalling pathways are activated through multiple mechanisms and appear to play a major role in melanoma development and progression.

OBJECTIVES

In this study, we examined whether targeting the MAPK and/or AKT signalling pathways would have therapeutic effects against melanoma.

METHODS

Using a panel of pharmacological inhibitors (BAY 43-9006, PD98059, U0126, wortmannin, LY294002) we inhibited the MAPK and AKT signalling pathways at different levels and evaluated the effects on growth, survival and invasion of melanoma cells in monolayer and organotypic skin culture.

RESULTS

Antiproliferative and proapoptotic effects of inhibitors alone in monolayer culture were disappointing and varied among the different cell lines. In contrast, combined targeting of the MAPK and AKT signalling pathways significantly inhibited growth and enhanced apoptosis in monolayer culture. To verify our data in a more physiological context we incorporated melanoma cells into regenerated human skin mimicking the microenvironment of human melanoma. Combinations of MAPK and AKT inhibitors completely suppressed invasive tumour growth of melanoma cells in regenerated human skin.

CONCLUSIONS

Combined targeting of MAPK and AKT signalling pathways is a promising strategy for melanoma treatment and should encourage further in-depth investigations.

Explosion characteristics of intense femtosecond-laser-driven water droplets

An efficient acceleration of energetic ions is observed when small heavy-water droplets of approximately 20 microm diameter are exposed to ultrafast (approximately 40 fs) Ti:sapphire laser pulses of up to 10(19) W/cm2 intensity. Quantitative measurements of deuteron and neutron spectra were done, allowing one to analyze the outward and inward directed deuteron acceleration from the droplet. Neutron spectroscopy based on the D (d,n) fusion reaction was accomplished in four different spatial directions. The energy shifts of those fusion neutrons produced inside the exploding droplet reflect a remaining deuteron acceleration inside the irradiated droplet along the axis of the incident laser beam. The overall neutron yield of the microdroplets is relatively small as a result of the dominant outward directed acceleration of the deuterons with 1200 neutrons/shot. Relying on the "explosion-like" acceleration of such spherical droplet targets we have developed a spray target consisting of heavy-water microspheres with diameters of 150 nm . Both the high deuteron energies of up to 1 MeV resulting from the irradiation intensity of approximately 10(19) W/cm2 as well as the collisions between the deuterons and the surrounding spray delivered about one order of magnitude more neutrons than the single-droplet system. The approximately 6 x 10(3) neutrons per laser pulse from the spray can be attributed to an efficient deuteron release from a significantly smaller laser excited volume as from deuterium-cluster targets.

Spectral dips in ion emission emerging from ultrashort laser-driven plasmas

Deep dips in MeV ion spectra are obtained from water droplet targets irradiated by intense [(0.5-1.2) x 10(19) W/cm(2)] and ultrashort (35 fs) laser pulses. The existence of these dips is ascribed to the generation of a multielectron-temperature plasma, which is confirmed by our experiments. An existing fluid model based on hot-electron components with significantly different temperatures is consistent with the behavior we observe in the ion spectra of the femtosecond laser-driven interaction. The model provides a good simulation of the observed spectral dips and allows us to establish important parameters such as hot- and cold-electron temperatures and the respective electron density ratios. The result may be of interest for spectral tailoring of proton spectra in future applications of laser-generated proton beams.

Transmission electron microscopy of fluorapatite-gelatine composite particles prepared using focused ion beam milling

In this paper, synthetic fluorapatite-gelatine composite particles are prepared for transmission electron microscopy (TEM) studies using two methods based on focused ion beam (FIB) milling. TEM studies on the FIB-prepared specimens are compared with TEM observations on samples prepared using an ultramicrotome. The results show that ultramicrotome slicing causes significant cracking of the apatite, whereas the ion beam can be used to make high-quality, crack-free specimens with no apparent ion beam-induced damage. The TEM observations on the FIB-prepared samples confirm that the fluorapatite composite particles are composed of elongated, preferentially orientated grains and reveal that the grain boundaries contain many small interstices filled with an amorphous phase.

Concomitant exposure of rainbow trout fry to Gyrodactylus derjavini and Flavobacterium psychrophilum: effects on infection and mortality of host

Although rainbow trout fry mortality syndrome caused by the bacterium Flavobacterium psychrophilum is widespread in fish farms it is difficult to reproduce infection of rainbow trout in the laboratory using immersion exposure with bacterial suspensions. It has therefore been speculated that ectoparasites could act as enhancers of bacterial infections under natural conditions. In the present study rainbow trout fry were exposed to infections with F. psychrophilum (immersion for 30 min or 10 h) alone, exposed to the ectoparasitic monogenean Gyrodactylus derjavini alone or exposed to both pathogens in combination. Infection levels and host mortality were subsequently monitored to elucidate if the ectoparasitic monogeneans could enhance infection of fish with the bacterium. Immersion of fish in bacterial suspensions alone did not result in infection. Only one fish became infected with the bacterium and this fish belonged to the combination exposure group. The parasite populations increased differently in the various groups and it was found that host mortality was correlated to gyrodactylid infection levels (r=0.94) but not to bacterial exposure. The results emphasise the pathogenicity of the parasite G. derjavini, the relative resistance of intact fish to direct exposure to F. psychrophilum but provide only a weak indication of a possible enhancement of bacterial invasion due to ectoparasitic infections. It cannot be excluded that higher parasite burdens and/or prolonged immersion (more than 10 h) in bacterial suspensions may result in bacterial invasion.

[Image quality and exposure dose in digital projection radiography]

PURPOSE

Comparison of the imaging capabilities of storage phosphor (computed) radiography and flat plate radiography with conventional film-screen radiography to find new strategies for quality and dose management, i. e., optimizing imaging quality and dose depending on the imaging method and clinical situation.

MATERIALS AND METHODS

Images of a CDRAD-phantom, hand-phantom, abdomen-phantom and chest-phantom obtained with different exposure voltages (50 kV, 73 kV, 109 kV) and different speeds (200, 400, 800, 1600) were processed with various digital systems (flat plate detector: Digital Diagnost [Philips]; storage phosphors: ADC-70 [Agfa], ADC-Solo [Agfa], FCR XG 1 [Fuji]) and a conventional film-screen system (HT100G/ Ortho Regular [Agfa]).

RESULTS

The evaluation of CDRAD images found the flat plate detector system to have the highest contrast detectability for all dose levels, followed by the FCR XG 1, ADC-Solo and ADC-70 systems. Comparison of the organ-phantom images found the flat plate detector system to be equal to film-screen radiography and especially to storage phosphor systems even for low exposure doses.

CONCLUSIONS

Flat plate radiography systems demonstrate the highest potential for high image quality when reducing the exposure dose. Depending on the system generation, the storage phosphor systems also show an improved image quality, but the possibility of a dose reduction is limited in comparison with the flat plate detector system.

Chasing a miracle: why infertile women continue to stay in treatment

This article discusses the reasons infertile couples continue to remain in infertility treatment. Through a qualitative research approach, using eight open-ended questions, the author interviewed a convenience sample of fourteen women in a large Midwestern academic health center reproductive endocrinology group practice, to identify reasons that influenced their decision to stay in treatment. The desire to have one's own children was the motivating force which helped sustain a sense of hope in these women fueled by the advanced technology advocated by their physicians. Support for these women were mostly from spouses and family members with friends with children not being very supportive. The lack of patient education was seen as a very negative influence by most of the participants.

Distinct modes of mature and precursor tRNA binding to Escherichia coli RNase P RNA revealed by NAIM analyses

We have analyzed by nucleotide analog interference mapping (NAIM) pools of precursor or mature tRNA molecules, carrying a low level of Rp-RMPalphaS (R = A, G, I) or Rp-c7-deaza-RMPalphaS (R = A, G) modifications, to identify functional groups that contribute to the specific interaction with and processing efficiency by Escherichia coli RNase P RNA. The majority of interferences were found in the acceptor stem, T arm, and D arm, including the strongest effects observed at positions G19, G53, A58, and G71. In some cases (interferences at G5, G18, and G71), the affected functional groups are candidates for direct contacts with RNase P RNA. Several modifications disrupt intramolecular tertiary contacts known to stabilize the authentic tRNA fold. Such indirect interference effects were informative as well, because they allowed us to compare the structural constraints required for ptRNA processing versus product binding. Our ptRNA processing and mature tRNA binding NAIM analyses revealed overlapping but nonidentical patterns of interference effects, suggesting that substrate binding and cleavage involves binding modes or conformational states distinct from the binding mode of mature tRNA, the product of the reaction.

Chemical synthesis and biological investigation of a 77-mer oligoribonucleotide with a sequence corresponding to E. coli tRNA(Asp)

A 77-mer RNA with the sequence of Eschlerichia coli tRNA(Asp) has been chemically synthesised using standard automated phosphoramidite chemistry with the coupling reagent 4,5-dicyanoimidazole (DCI). The synthesis was carried out on a 1000 A CPG-column and. after deprotection and gel purification, a yield of about 7 mmol with a purity of > 95% was reproducibly obtained. By comparing automated synthesis of the 77-mer RNA using 1H-tetrazole and DCI as activator, DCI is advantageous in producing longer RNAs. However, for shorter RNAs ( <40 mer) no difference could be observed. In addition to the all-ribo tRNA(Asp) carrying the wild-type sequence, two variants were synthesised, one with a single C to G48 mutation and the second with a 2'-deoxy modification at C48. The three tRNAs were tested for their aminoacylation efficiency and high affinity binding to E. coli RNase P RNA. The results demonstrate that chemically synthesised 77-mer oligoribonucleotides can be successfully used for structure function studies.

Regulation of the Aspergillus nidulans hisB gene by histidine starvation

The hisB gene of the filamentous fungus Aspergillus nidulans encodes imidazole glycerol-phosphate dehydratase (E.C. 4.2.1.19), which catalyses the seventh enzymatic step in histidine biosynthesis. The gene was isolated and its deduced peptide sequence of 247 amino acids showed up to 54% identity with the IGPD enzymes of organisms comprising all three kingdoms. Expression of hisB cDNA in a Saccharomyces cerevisiae his3delta mutant strain functionally complemented the growth phenotype under histidine limitation. Addition of histidine did not affect hisB mRNA levels in A. nidulans wild-type cells. Histidine starvation conditions increased the hisB transcript level four-fold, suggesting regulation by a cross-pathway regulatory network. Deletion of the complete hisB open reading frame in A. nidulans strain A234 resulted in histidine auxotrophy. Additionally, hisB deletion strains were blocked from sexual fruiting body formation on medium containing low concentrations of histidine. This developmental phenotype of the hisB deletion mutant strain correlated with the induction of the cross-pathway control system.

G protein beta 3 gene: structure, promoter, and additional polymorphisms

Recent studies have shown that a polymorphism (C825T) in the gene encoding the G protein beta 3 subunit (GNB3) is associated with hypertension and obesity. We characterized the entire GNB3 gene, which spans 7.5 kb and is composed of 11 exons and 10 introns. Its promoter lacks a TATA box but harbors GC-rich regions. The functional activity of the GNB3 promoter was verified with reporter gene assays that also demonstrated its inducibility by phorbol esters. A novel polymorphism in the promoter region A(-350)G occurred with frequencies (G allele) of 76%, 97%, and 61% in Africans, Chinese, and Germans, respectively. Reporter gene constructs with either the A or the G allele did not differ with regard to inducement of the reporter protein. A silent nucleotide exchange in the coding region (A657T) occurred with T allele frequencies ranging from 0.5% to 2.4%. Another polymorphism (G814A) results in the replacement of glycine by serine at position 272. In Germans, the A allele occurred at a frequency of 10%. Finally, a C1429T polymorphism in the 3' untranslated region of GNB3 was identified that occurred at T allele frequencies of 38%, 17%, and 30% in Africans, Chinese, and Germans, respectively. Haplotype prediction indicated in Germans an almost complete association of GNB3 825T with 1429T, and vice versa. An analysis of these polymorphic loci in nonhuman primates revealed that the ancestral GNB3 gene harbored the (-350)G, 825C, and 1429C alleles. This is the first complete characterization of the human GNB3 gene and its promoter region, which will enable refined epidemiological and biochemical investigations of GNB3 in hypertension and obesity.

Differential role of the intermolecular base-pairs G292-C(75) and G293-C(74) in the reaction catalyzed by Escherichia coli RNase P RNA

We present a systematic investigation of the thermodynamic and kinetic role of the intermolecular G292-C(75 )and G293-C(74 )Watson-Crick base-pairs in the reaction catalyzed by Escherichia coli RNase P RNA. Single turnover kinetics were analyzed for wild-type RNase P RNA and two variants with a single G to C exchange (C292 or C293), either acting on wild-type precursor tRNA (ptRNA) or derivatives carrying a complementary change at the tRNA 3'-end (G(74)CA or CG(75)A). Ground state binding of tRNA was studied using three different methods, including a novel fluorescence-based assay measuring equilibrium binding. We conclude that: (1) the role of the G293-C(74 )interaction is essentially confined to Watson-Crick base-pairing, with no indication for crucial tertiary contacts involving this base-pair; (2) the G293-C(74 )pair, although being as important for ptRNA ground state binding as G292-C(75), is much less crucial to catalytic performance than the G292-C(75) pair; (3) disruption of the G292-C(75 )base-pair results in preferential destabilization of enzyme transition-state complexes; and (4) the identity of the G292-C(75) pair, as part of the higher-order structural context consisting of coplanar G292-C(75)-A258 and G291-G259-A(76 )triples, contributes to high affinity binding of ptRNA and catalytic efficiency.

Export and transport of tRNA are coupled to a multi-protein complex

Vigilin is a ubiquitous multi heterogeneous nuclear ribonucleoprotein (hnRNP) K homologous (KH)-domain protein. Here we demonstrate that purified recombinant human vigilin binds tRNA molecules with high affinity, although with limited specificity. Nuclear microinjection experiments revealed for the first time that the immuno-affinity-purified nuclear vigilin core complex (VCC(N)) as well as recombinant vigilin accelerate tRNA export from the nucleus in human cells. The nuclear tRNA receptor exportin-t is part of the VCC(N). Elongation factor (EF)-1alpha is enriched in VCC(N) and its cytoplasmic counterpart VCC(C), whereas EF-1beta, EF-1gamma and EF-1delta are basically confined to the VCC(C). Our results suggest further that vigilin and exportin-t might interact during tRNA export, provide evidence that the channeled tRNA cycle is already initiated in the nucleus, and illustrate that intracellular tRNA trafficking is associated with discrete changes in the composition of cellular cytoplasmic multi-protein complexes containing tRNA.

Changes in EEG power spectra during biofeedback of slow cortical potentials in epilepsy

The goal of the study was to explore parallel changes in EEG spectral frequencies during biofeedback of slow cortical potentials (SCPs) in epilepsy patients. Thirty-four patients with intractable focal epilepsy participated in 35 sessions of SCP self-regulation training. The spectral analysis was carried out for the EEG recorded at the same electrode site (Cz) that was used for SCP feedback. The most prominent effect was the increase in the theta 2 power (6.0-7.9 Hz) and the relative power decrement in all other frequency bands (particularly delta 1, alpha 2 and beta 2) in transfer trials (i.e., where patients controlled their SCPs without continuous feedback) compared with feedback trials. In the second half of the training course (i.e., sessions 21-35) larger power values in the delta, theta, and alpha bands were found when patients were required to produce positive versus negative SCP shifts. Both across-subject and across-session (within-subject) correlations between spectral EEG parameters, on the one hand, and SCP data, on the other hand, were low and inconsistent, contrary to high and stable correlations between different spectral variables. This fact, as well as the lack of considerable task-dependent effects during the first part of training, indicates that learned SCP shifts did not directly lead to the specific dynamics of the EEG power spectra. Rather, these dynamics were related to nonspecific changes in patients' brain state.

Identification and characterization of ComE and ComF, two novel pilin-like competence factors involved in natural transformation of Acinetobacter sp. strain BD413

Although the high level of competence for natural transformation of Acinetobacter sp. strain BD413 has been the subject of numerous studies, only two competence genes, comC and comP, have been identified to date. By chromosomal walking analysis we found two overlapping open reading frames, designated comE and comF, starting 61 bp downstream of comC. comE and comF are expressed as stable proteins in Escherichia coli, thus proving that they are indeed coding regions, but expression was successful only with 5'-deleted genes. ComE and ComF are similar to pilins and pilin-like components. Both genes were mutated, and the phenotypes of the mutants were analyzed. Natural transformation in comF mutants is 1,000-fold reduced, whereas comE mutants exhibit 10-fold-reduced transformation frequencies. This is clear evidence that comE and comF are involved in natural transformation. However, ComE and ComF are specific for DNA translocation, since comE and comF defects affected neither piliation nor lipase secretion. These results suggest that the type IV pili, the general protein secretion pathway, and the DNA translocation machinery in Acinetobacter sp. strain BD413 are evolutionary related but functionally distinct systems.

Role of metal ions in the hydrolysis reaction catalyzed by RNase P RNA from Bacillus subtilis

Precursor tRNA (ptRNA) substrates carrying a single Rp or Sp-phosphorothioate modification at the RNase P cleavage site were used as tools to study the cleavage mechanism of RNase P RNA from Bacillus subtilis. Both the Sp and the Rp-diastereomer reduced the rate of processing at least 10(4)-fold under conditions where the chemical step is essentially rate-limiting. Neither the Rp nor the Sp-phosphorothioate modification affected ptRNA ground state binding to B. subtilis RNase P RNA. Processing of the Rp-diastereomeric ptRNA could be restored in the presence of Mn2+or Cd2+, demonstrating direct metal ion coordination to the pro -Rp oxygen during catalysis. With Cd2+, processing required the presence of another metal ion, such as Ca2+or Mg2+, to mediate substrate binding. This is in contrast to Escherichia coli RNase P RNA, which promotes cleavage of Rp-diastereomeric ptRNA in the presence of Cd2+as the sole divalent metal ion. Analysis of [Cd2+]-dependent processing of the Rp-diastereomeric substrate by B. subtilis RNase P RNA was consistent with the involvement of at least two metal ions in catalysis. The presence of two catalytic metal ion binding sites is also supported by the inhibition mode of Ca2+on cleavage of unmodified ptRNA. In the presence of an Sp-phosphorothioate modification at the scissile bond, neither Mn2+nor Cd2+were able to restore significant cleavage at this location. Instead, the ribozyme promotes cleavage at the neighboring unmodified phosphodiester with low efficiency. Unaffected ground state binding of the Sp-diastereomeric ptRNA but a >/=10(4)-fold reduced hydrolysis rate may indicate a crucial role of the pro -Sp oxygen in transition state stabilization or may be attributed to steric exclusion of catalytic metal ions. Based on our comparative analyses of B. subtilis and E. coli RNase P RNA, each representing the main structural subtypes of bacterial RNase P RNA, common features in terms of active site constraints and role of catalytic metal ions can now be formulated for bacterial RNase P RNAs. On the other hand, substantial and unexpected differences with respect to the overall metal ion requirements and tRNA binding modes have been observed for the two catalytic RNAs.