bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave‐Assisted Direct Synthesis and Polymerization of Chiral Acrylamide
Authors: Iannelli Mauro , Ritter Helmut
Published: February 2005

Summary: Chiral (R)‐N‐(1‐phenylethyl)‐acrylamide (3) was synthesized directly from acrylic acid (1) and (R)‐1‐phenylethylamine (2) via microwave irradiation without any further activation and in a solvent‐free medium. The kinetic measurements performed show high selectivity and conversion to the amide after only few minutes of reaction time. It was possible to obtain optically active polymers containing both acrylamide and imide structural units in a one‐pot reaction starting from acrylic acid (1), amine (2) and AIBN as a free radical initiator. The same reactions were evaluated by classical thermal heating in an oil bath and the results are compared.

The condensation reaction between acrylic acid and (R)‐1‐phenylethylamine by MW irradiation in the presence and absence of AIBN as a free radical initiator.

magnified image

The condensation reaction between acrylic acid and (R)‐1‐phenylethylamine by MW irradiation in the presence and absence of AIBN as a free radical initiator.
Evidence for the presence of α1 adrenoceptor subtypes in the human ureter
Authors: Sigala Sandra , Dellabella Marco , Milanese Giulio , Fornari Sara , Faccoli Stefania , Palazzolo Francesca , Peroni Angelo , Mirabella Giuseppe , Cunico Sergio Cosciani , Spano PierFranco , Muzzonigro Giovanni
Published: February 2005

Aim

Several studies have proposed a role for α1 adrenoceptors (ARs) in ureteral physiology, indicating that they are present in the ureter; however, few studies have been done to identify α1 AR subtypes present in this area. Thus, this study was carried out to characterize the α1 AR subtype gene and protein expression in proximal, medial, and distal region of the human ureter.

Methods

Molecular characterization of α1 AR subtypes were analyzed by semi‐quantitative RT‐PCR. α1 AR protein expression was studied by saturation binding curves and by competition binding curves with selective antagonists. Analysis of data was performed using the GraphPad PRISM 4 software.

Results

Analysis of saturation binding curves revealed a heterogeneous distribution of α1 AR binding sites, the Bmax for the distal ureter was indeed 52.5 ± 5.4 fmol/mg prot, while a lower similar density of α1 ARs was demonstrated in the medial (25.2 ± 1.7 fmol/mg prot) and proximal (23.4 ± 0.4 fmol/mg prot) ureters. Molecular and pharmacological characterization of α1 AR subtypes indicated that each receptor was present, although with differences in terms of the amount expressed.

Conclusions

Human ureter was endowed with each α1 AR subtype, although α1D and α1A ARs were prevalent over α1B ARs. Radioligand binding results revealed that there were no significant differences in the Kd between ureteral regions, while a heterogeneous distribution of α1 AR binding sites was detected, with the highest density of α1 ARs in the distal ureter and a lower similar density in the medial and proximal ureters. Neurourol. Urodynam. 24:142–148, 2005. © 2005 Wiley‐Liss, Inc.
Smooth muscle membrane organization in the normal and dysfunctional human urinary bladder: A structural analysis
Authors: Burkhard Fiona C. , Monastyrskaya Katia , Studer Urs E. , Draeger Annette
Published: February 2005

Purpose

The decline in contractile properties is a characteristic feature of the dysfunctional bladder as a result of infravesical outlet obstruction. During clinical progression of the disease, smooth muscle cells undergo structural modifications. Since adaptations to constant changes in length require a high degree of structural organization within the sarcolemma, we have investigated the expression of several proteins, which are involved in smooth muscle membrane organization, in specimens derived from normal and dysfunctional organs.

Materials and Methods

Specimen from patients with urodynamically normal/equivocal (n = 4), obstructed (n = 2), and acontractile (n = 2) bladders were analyzed relative to their structural features and sarcolemmal protein profile.

Results

Smooth muscle cells within the normal urinary bladder display a distinct sarcolemmal domain structure, characterized by firm actin‐attachment sites, alternating with flexible “hinge” regions. In obstructed bladders, foci of cells displaying degenerative sarcolemmal changes alternate with areas of hypertrophic cells in which the membrane appears unaffected. In acontractile organs, the overall membrane structure remains intact, however annexin 6, a protein belonging to a family of Ca2+‐dependent, “membrane‐organizers,” is downregulated.

Conclusion

Degenerative changes in smooth muscle cells, which are chronically working against high resistance, are preferentially located within the actin‐attachment sites. In acontractile bladders, the downregulation of annexin 6 might have a bearing on the fine‐tuning of the plasma membrane during contraction/relaxation cycles. Neurourol. Urodynam. 24:128–135, 2005. © 2005 Wiley‐Liss, Inc.
A computational stream function method for two‐dimensional incompressible viscous flows
Authors: Kobayashi Marcelo H. , Pereira José Manuel C.
Published: February 2005

This work concerns the development of a numerical method based on the stream function formulation of the Navier–Stokes equations to simulate two‐dimensional—plane or axisymmetric—viscous flows. The main features of the proposed method are: the use of the high order finite‐difference compact method for the discretization of the stream function equation, the implicit pseudo‐transient Newton–Krylov‐multigrid matrix free method for the stationary stream function equation and the fourth order Runge–Kutta method for the integration of non‐stationary flows. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetic studies on the thermal polymerization of N‐chloroacetyl‐11‐aminoundecanoate potassium salt
Authors: Ramis Xavier , Salla Josep María , Puiggalí Jordi
Published: February 2005

A potassium salt of N‐chloroacetyl‐11‐aminoundecanoate was thermally polymerized to obtain the corresponding poly(glycolic acid‐alt‐11‐aminoundecanoic acid). A kinetic study was then performed that was based on isothermal and nonisothermal polymerizations performed in a differential scanning calorimeter. The complete kinetic triplet was determined (the activation energy, pre‐exponential factor, and integral function of the degree of conversion). A kinetic analysis was performed with an integral isoconversional procedure (free model), and the kinetic model was determined both with the Coats–Redfern method (the obtained isoconversional value being accepted as the effective activation energy) and through the compensation effect. The polymerization followed a three‐dimensional growth‐of‐nuclei (Avrami) kinetic mechanism. Isothermal polymerization was simulated with nonisothermal data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1166–1176, 2005
Inhomogeneity control in polymer gels
Authors: Ikkai Fumiyoshi , Shibayama Mitsuhiro
Published: February 2005

Inhomogeneities, that is, nonrelaxing frozen concentration fluctuations, are inevitably present in polymer gels because they are introduced during the crosslinking of the constituent polymer chains in a solvent. Therefore, inhomogeneities increase as the number of crosslinks increases in a gel. The ionization of polymer gels is one of the methods used to suppress inhomogeneities. However, because crosslinking also means a freezing‐in of the conformation and topology of polymer chains in a solvent according to the chemistry of crosslinking, inhomogeneity control is quite sophisticated. In this article, we discuss the relationship between the inhomogeneities and the molecular/environmental parameters of polymer gels, such as the polymer concentration, the degree of crosslinking, the degree of ionization, and the interaction parameter, by considering the memory effect of gels. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 617–628, 2005
Effects of poly(N‐isopropylacrylamide) on the solution properties of hydrophobically modified acrylamide copolymer
Authors: Duan Ming , Hu Xingqi , Ren Dongmei
Published: February 2005

The hydrophobic interaction between hydrophobically modified acrylamide copolymer (HMPAM) and poly(N‐isopropylacrylamide) (PNIPAM) in aqueous solutions was investigated. The results show that the solution properties of HMPAM are significantly influenced by the addition of PNIPAM. In dilute regime, the intrinsic viscosity of HMPAM in 0.025 wt % PNIPAM/0.1 M NaCl mixed solution is 17.52 dL g−1, about 2 times 8.66 dL g−1, that in 0.1 M NaCl solution, which is due to the attractive interaction between the hydrophobic parts of PNIPAM and HMPAM molecules. In semidilute regime, below the saturation concentration, the addition of PNIPAM can lead to both the apparent viscosity and the modulus of HMPAM solutions increasing, which is attributed to the number of aggregation junctions increasing, responsible for the increase of the contribution of the reversible network to the viscosity increase, the β value. In addition, a thermothickening behavior for the HMPAM/PNIPAM mixed solution is observed with increasing temperature over 15–30 °C, which is consistent with the large increase of the Huggins coefficient of HMPAM in the presence of PNIPAM from 1.95 to 7.59 as temperature increases from 25 to 30 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 709–715, 2005
Progress and challenges in high‐resolution refinement of protein structure models
Authors: Misura Kira M.S. , Baker David
Published: February 2005

Achieving atomic level accuracy in de novo structure prediction presents a formidable challenge even in the context of protein models with correct topologies. High‐resolution refinement is a fundamental test of force field accuracy and sampling methodology, and its limited success in both comparative modeling and de novo prediction contexts highlights the limitations of current approaches. We constructed four tests to identify bottlenecks in our current approach and to guide progress in this challenging area. The first three tests showed that idealized native structures are stable under our refinement simulation conditions and that the refinement protocol can significantly decrease the root mean square deviation (RMSD) of perturbed native structures. In the fourth test we applied the refinement protocol to de novo models and showed that accurate models could be identified based on their energies, and in several cases many of the buried side chains adopted native‐like conformations. We also showed that the differences in backbone and side‐chain conformations between the refined de novo models and the native structures are largely localized to loop regions and regions where the native structure has unusual features such as rare rotamers or atypical hydrogen bonding between β‐strands. The refined de novo models typically have higher energies than refined idealized native structures, indicating that sampling of local backbone conformations and side‐chain packing arrangements in a condensed state is a primary obstacle. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Buoyancy-driven propagation of an isolated fluid-filled crack in rock: implication for fluid transport in metamorphism
Authors: Nakashima Yoshito
Published: February 2005

A new model for upward transport of buoyant fluid released during metamorphism is proposed. The model is fluid transport by buoyancy-driven propagation of isolated fluid-filled cracks. The mechanical behavior of a two-dimensional, isolated, vertical, and fluid-filled crack in impermeable rock is investigated using linear fractire mechanics and fluid dynamics. The results show that steady-state crack propagation which causes long-distance transport of the fluid occurs when the vertical cross-sectional area of the crack exceeds a critical value. Propagation velocity and average thickness of the crack under the steady-state propagation regime are expressed explicitly by the following seven parameters: vertical crack length; rigidity, Poisson's ratio, and fracture toughness of the rock; fluid viscosity; density difference between the rock and the fluid; gravitational acceleration. An isolated H2O-filled crack of vertical length 100 m, for example, propagates upwards in the crust at ∼0.3 m/s with the average thickness ∼0.2 mm when the following likely values are assumed: 0.1 mPa s for the H2O viscosity; 3 MPa m1/2 for the fracture toughness of the crustal rock. The application of the obtained results to the transport of H2O released during metamorphism suggests that the number density of isolated cracks propagating in the crust is very low. Since the propagation velocity is high, our model is suitable particularly for fluid transport through hot quartz-rich rock where fluid-filled cracks have geologically short lifetimes.
Cognitive impairment in patients with chronic hepatitis treated with interferon alpha (IFNα): results from a prospective study
Authors: Lieb Klaus , Engelbrecht Marc A. , Gut Oliver , Fiebich Bernd L. , Bauer Joachim , Janssen Gesa , Schaefer Martin
Published: February 2005

Background.

Treatment with low-dose interferon alpha (IFN-α) is often associated with neuropsychiatric side effects. In addition to depression and anxiety, IFN-α associated cognitive impairment significantly affects patient’s mental health and quality of life.

Aims of the study.

To measure possible effects of low-dose IFN-α on cognitive functioning and its relationship to the development of depression and anxiety.

Method.

We prospectively followed 38 patients with a chronic hepatitis B or C by neuropsychological tests and psychiatric self-rating scales during 12 weeks of low-dose treatment with IFN-α.

Results.

Before IFN-α treatment, neuropsychological tests as well as self-ratings in the Beck’s Depression Inventory (BDI), the Hospital Anxiety and Depression Scale (HADS) and the Self-Report Symptom Inventory 90 Items-Revised (SCL-90-R) were within the normal range. Following 12 weeks of treatment with IFN-α resulted in a slight, but significant increase in depression scores. Neuropsychological assessment after 12 weeks of IFN-α treatment showed a significant decrease of the immediate recall in the Auditory-Verbal Learning Test (AVLT) and a significant reduction of words recited in the Controlled Oral Word Association Test (COWA). Cognitive impairment did not significantly correlate with depressive symptoms or anxiety.

Conclusion.

Our results indicate that even low-dose IFN-α induces cognitive impairment independent from depressive symptoms, which might be related to functional disturbances in the prefrontal cortex and the hippocampus. We suggest close monitoring of cognitive function during IFN-α treatment of chronic hepatitis.
Identification of the sucrose non‐fermenting related kinase SNRK, as a novel LKB1 substrate
Authors: Jaleel Mahaboobi , McBride Andrew , Lizcano Jose M. , Deak Maria , Toth Rachel , Morrice Nick A , Alessi Dario R.
Published: February 2005

Recent work has shown that the LKB1 tumour suppressor protein kinase phosphorylates and activates protein kinases belonging to the AMP activated kinase (AMPK) subfamily. In this study, we identify the sucrose non‐fermenting protein (SNF1)‐related kinase (SNRK), a largely unstudied AMPK subfamily member, as a novel substrate for LKB1. We demonstrate that LKB1 activates SNRK by phosphorylating the T‐loop residue (Thr173), and that the LKB1 regulatory subunits STRAD and MO25 are required for LKB1 to activate SNRK. We find that SNRK is not active when expressed in HeLa cells that lack expression of LKB1, and its activity is restored by expression of wild type LKB1, but not catalytically deficient LKB1. We also present evidence that two other AMPK‐related kinases more distantly related to AMPK than SNRK, namely NIM1 and testis‐specific serine/threonine kinase‐1 (TSSK1) are not substrates for LKB1. Tissue distribution analysis indicates that SNRK protein is mainly expressed in testis, similar to TSSK isoforms, whereas NIM1 is more widely expressed. These results provide evidence that SNRK could mediate some of the physiological effects of LKB1.
The fidelity of DNA synthesis by human immunodeficiency virus type 1 reverse transcriptase increases in the presence of polyamines
Authors: Bakhanashvili Mary , Novitsky Elena , Levy Itzchak , Rahav Galia
Published: February 2005

The high error rates characteristic of human immunodeficiency virus type‐1 reverse transcriptase (HIV‐1 RT) are a presumptive source of the viral hypervariability that substantially affect viral pathogenesis and resistance to drug therapy. We have analyzed the potential role of polyamines in the fidelity of DNA synthesis by HIV‐1 RT. The current study suggest that polyamines tested has the potential to be “antimutator”. The polyamines exert the ability to reduce the misincorporation and mispair extension with both RNA/DNA and DNA/DNA template‐primers in the following order: spermine >
spermidine >
putrescine. In view of the significance of mutations of HIV, the possible roles of polyamines in the accuracy of DNA synthesis could be of particular importance; polyamines may affect the mutation rate of the virus.
Evolution of different oligomeric glycyl‐tRNA synthetases
Authors: Tang Su-Ni , Huang Jing-Fei
Published: February 2005

There are two oligomeric types of glycyl‐tRNA synthetases (GlyRSs) in genome, the α2β2 tetramer and α2 dimer. Here, we showed that the anticodon‐binding domains (ABDs) of dimeric and tetrameric GlyRSs are non‐homologous, although their catalytic central domains (CCDs) are homologous. The dimeric GlyRS_ABD is fused to the C‐terminal of CCD in α‐subunit, but the tetrameric GlyRS_ABD is to the C‐terminal in β‐subunit during evolution. Generally, one species only contains one oligomeric type of GlyRS, but the both oligomeric GlyRSs with the multiple homologous domains can be observed in Magnetospirillum magnetotacticum genome, nevertheless, these homologous domains are probably from different genomes.
Genetic thrombophilias and uterine artery Doppler velocimetry and preeclampsia
Authors: Driul L. , Damante G. , D'Elia A. , Ianni A. , Springolo F. , Marchesoni D.
Published: February 2005

Objective

The aim of this study was to evaluate the correlation between genetic thrombophilic mutations, uterine artery Doppler at 24 weeks of gestation and preeclampsia.

Methods

In a case control study we performed the genetic analysis for Leiden mutation of factor V gene (FV), G20210A mutation of the prothrombin gene (PT) and C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene in 103 women that had already attended routine ultrasonography scanner at 20 weeks at our Department.

Results

The frequency of heterozygous carriers of the factor V Leiden was 17.4% in the women with preeclampsia and abnormal artery Doppler compared with 3.12% in the patients with normal pregnancies. This difference was statistically significant (P<0.05). The frequency of mutation G20210A of prothrombin gene was 1.5 vs. 4.3% between women with normal pregnancies and with preeclampsia. This difference is not statistically significant. The frequency of homozygous patients for the C677T mutation of MTHFR gene among the patients with preeclampsia was 21.7% and in the control group was 10.3%, but this difference is not statistically significant. No thrombophilic gene variants were found in women with preeclampsia and normal uterine artery Doppler.

Conclusion

We demonstrated the important association between factor V Leiden mutation, abnormal uterine Doppler at 24 weeks and preeclampsia in our population.
Support for Democracy in Eastern and Western Germany: an Attempt to Explain the Differences
Authors: POLLACK DETLEF
Published: February 2005

This paper raises the question to what extent of East Germans support the political system in which they live. Have people who lived for decades under authoritarian conditions been able to develop a democratic culture? Or are their mind-sets and attitudes still influenced by the effects of GDR socialization with its socialist values and ideals? The paper argues that the peculiarities of the political culture in East Germany are less attributable to effects of GDR socialization than to current differences in the economic situation between East and West Germany.
The Mobilisation of the European Left in the early 21st Century
Authors: AZMANOVA ALBENA
Published: February 2005

This study discerns peculiarities in the electoral mobilisation in EU member states in recent years and examines the effect of current social transformations on political discourse and voting behaviour. The overall change is traced to the emergence of opportunity-vs-risk vectors of political identification, challenging the capital vs labour dynamics of conflict. The decline in electoral support for traditional Left parties is attributed to the failure of the European Left to adjust to this realignment.
Molecular determination of the origin of acephalic cysticercus
Authors: CHUNG J.-Y. , KHO W.-G. , HWANG S.-Y. , JE E.-Y. , CHUNG Y.-T. , KIM T.-S. , EOM K.-S. , SOHN W.-M. , CHO S.-Y. , KONG Y.
Published: February 2005

Acephalic cysticercus (Ac), a rarely developed multilobulated and nonencysted form of larvalTaenia, causes hydrocephalus or adhesive arachnoiditis in the ventricles and subarachnoidal space that often lead to fatal outcome in affected patients. Ac has been proposed to originate fromT. soliumon the basis of morphological features, while no molecular data supporting the presumption have been available. In the present study, we investigated the immunological properties as well as molecular characteristics of Ac that was obtained surgically from 6 patients. Immunoblotting of the cyst fluid from Ac samples demonstrated the constitutive expression of aT. soliummetacestode (TsM) 10 kDa protein. Specific antibodies against the truncated 10 kDa protein, which appears to be species specific for TsM cysticercosis, were detected in both serum and cerebrospinal fluid samples of Ac patients. Nucleotide sequences of mitochondrial cytochromecoxidase subunit I (COI) and NADH dehydrogenase subunit 1 (ND1) genes of Ac were almost identical to those ofT. soliumbut differed substantially from those of the otherTaeniaspecies. In phylogenetic analysis, Ac clustered withT. soliumin a well-supported clade. Our results strongly suggest that Ac may have originated fromT. solium.
Effects of host habitat quality on the viability of Cryptocotyle lingua (Trematoda: Digenea) cercariae
Authors: CROSS M. A. , IRWIN S. W. B. , FITZPATRICK S. M.
Published: February 2005

In an earlier study it was shown that Cryptocotyle lingua cercariae, matured in Littorina littorea from a polluted marine lagoon, displayed slower horizontal swimming rates, and reduced longevity compared to cercariae released by periwinkles from a cleaner environment. This work investigated whether the pollution-induced reduction in swimming rates was due to an inefficient swimming action or the adoption of a less direct swimming path. In addition, cercariae from L. littorea that had been transferred from an ‘unpolluted’ to a ‘polluted’ site for 1 month provided information on the speed with which pollutants affect cercariae through their intermediate hosts. Results indicated that, in general, horizontal swimming rates were reduced due to slower swimming rather than disorientation and longer swimming pathways. Effects of host transplantation to a polluted site were clearly evident after 1 month. Evidence suggested that the pollutants accumulated by the cercariae via their first intermediate host affected the neuromusculature associated with swimming performance rather than sensory structures. Bearing in mind the reduced viability of C. lingua cercariae in polluted sites it is assumed that high prevalence of this digenean in gastropods (at such sites) must be due to their continual introduction by infected birds attracted to these habitats from other areas.
Chronology of parasite-induced alteration of fish behaviour: effects of parasite maturation and host experience
Authors: SHIRAKASHI S. , GOATER C. P.
Published: February 2005

We monitored temporal changes in the magnitude of altered host behaviour in minnows (Pimephales promelas) experimentally infected with metacercariae of a brain-encysting trematode (Ornithodiplostomum ptychocheilus). This parasite develops and then encysts in a region of the brain that mediates the optomotor response (OMR), an innate behaviour that links visual stimuli with motor performance. The OMR of infected and uninfected minnows was evaluated between 0 and 10 weeks post-infection (p.i.), an interval spanning the development period of metacercariae to infectivity in birds. Trials involved monitoring the time an individual minnow spent following a spinning drum that had been painted with alternating black and white stripes. At 2 and 4 weeks p.i., infected minnows followed the drum 40% less often than controls. Differences between controls and infected fish declined thereafter, and were undetectable by 10 weeks p.i. Both control and infected fish habituated equally rapidly to the spinning drum. However, the difference in performance between controls and infected fish was 29% for experienced fish and 48% for fish that had never experienced the drum. Because maximum parasite-induced reduction in OMR coincided with the period of maximum parasite development, the behavioural effects are most likely due to unavoidable pathology in the brain associated with developing larvae.
Characterization of SSU and LSU rRNA genes of threeTrypanosoma (Herpetosoma) grosiisolates maintained in Mongolian jirds
Authors: SATO H. , OSANAI A. , KAMIYA H. , OBARA Y. , JIANG W. , ZHEN Q. , CHAI J. , UNE Y. , ITO M.
Published: February 2005

Trypanosoma (Herpetosoma) grosi, which naturally parasitizesApodemusspp., can experimentally infect Mongolian jirds (Meriones unguiculatus). Three isolates fromA. agrarius,A. peninsulae, andA. speciosus(named SESUJI, HANTO, and AKHA isolates, respectively) of different geographical origin (AKHA from Japan, and the others from Vladivostok), exhibited different durations of parasitaemia in laboratory jirds (2 weeks for HANTO, and 3 weeks for the others). To assess the genetic background of theseT. grosiisolates, their small (SSU) and large subunit (LSU) ribosomal RNA genes (rDNA) were sequenced along with those of 2 otherHerpetosomaspecies from squirrels. The SSU rDNA sequences of these 3 species along with available sequences of 3 otherHerpetosomatrypanosomes (T. lewisi,T. musculiandT. microti)seemed to reflect well the phylogenetic relationship of their hosts. Three isolates ofT. grosiexhibited base changes at 2–6 positions of 2019-base 18S rDNA, at 5–29 positions of 1817/1818-base 28Sα rDNA, or 1–5 positions of 1557–1559-base 28Sβ rDNA, and none was separated from the other 2 isolates by rDNA nucleotide sequences. Since base changes ofHerpetosomatrypanosomes at the level of inter- and intra-species might occur frequently in specified rDNA regions, the molecular analysis on these regions of rodent trypanosomes could help species/strain differentiation and systematic revision ofHerpetosomatrypanosome species, which must be more abundant than presently known.
Low‐energy neutral atom signatures of magnetopause motion in response to southward Bz
Authors: Collier Michael R. , Moore Thomas E. , Fok Mei‐Ching , Pilkerton Benjamin , Boardsen Scott , Khan Hina
Published: February 2005

We report an event observed by the Low‐Energy Neutral Atom (LENA) imager on 18 April 2001, in which enhanced neutral atom emission was observed coming from the direction of the Sun and from the general direction of the subsolar magnetopause. The enhanced neutral atom emission is shown to be primarily a result of increased solar wind charge exchange with the Earth's hydrogen exosphere, that is, enhanced neutral solar wind formation, occurring in conjunction with a southward turning of the interplanetary magnetic field (IMF) which moves the magnetopause closer to the Earth. It is shown that the neutral atom flux under compressed magnetopause conditions is extremely sensitive to changes in the IMF north‐south component.
Introduction to the special section: Violent Sun‐Earth connection events of October–November 2003
Authors: Gopalswamy N. , Barbieri L. , Lu G. , Plunkett S. P. , Skoug R. M.
Published: February 2005

During 2003 October and November, a series of solar eruptions occurred from three solar active regions. Some of these eruptions were extreme in terms of their origin (source properties) and heliospheric consequences. This paper summarizes the first results of the analysis of these violent Sun‐Earth connection events.
Acidosis Causes Endoplasmic Reticulum Stress and Caspase-12-Mediated Astrocyte Death
Authors: Aoyama Koji , Burns David M , Suh Sang Won , Garnier Philippe , Matsumori Yasuhiko , Shiina Hiroaki , Swanson Raymond A
Published: February 2005

Endoplasmic reticulum (ER) stress leads to activation of caspase-12, which in turn can lead to activation of caspase-3 and cell death. Here we report that transient acidosis induces ER stress and caspase-12-mediated cell death in mouse astrocytes. After a 3-hour incubation at pH 6.0, astrocytes exhibited delayed cell death associated with nuclear condensation and fragmentation. Cell death was reduced by the protein synthesis inhibitor cycloheximide, further suggesting an active cell death program. Acidosis increased the expression of the ER chaperone protein GRP-78, indicative of ER stress. Acidosis also increased caspase-12 mRNA expression, caspase-12 protein expression, cleavage of caspase-12 to its active form, and activation of caspase-3. Each of these effects was suppressed in astrocytes pretreated with caspase-12 antisense phosphorodiamidate morpholino oligodeoxynucleotides (PMOs). Caspase-12 antisense PMOs also reduced the cell death induced by acidosis. Immunoprecipitation studies showed dissociation of both caspase-12 and Ire1-α from GRP-78, thereby suggesting a mechanism by which acidosis can initiate the ER stress response. To evaluate caspase-12 activation in vivo, rats were subjected to middle cerebral artery ischemia–reperfusion. Immunostaining of brain sections harvested 24 hours later showed increased caspase-12 expression and nuclear condensation in astrocytes of the periinfarct region exposed to acidosis during ischemia. These findings suggest that acidosis induces ER stress and caspase-12 activation, and that these changes may contribute to delayed cell death after ischemia.
Ischemic Nitric Oxide and Poly (ADP-Ribose) Polymerase-1 in Cerebral Ischemia: Male Toxicity, Female Protection
Authors: McCullough Louise D , Zeng Zhiyuan , Blizzard Kathleen K , Debchoudhury Indira , Hurn Patricia D
Published: February 2005

It is well established that tissue damage and functional outcome after experimental or clinical stroke are shaped by biologic sex. We investigated the novel hypothesis that ischemic cell death from neuronally derived nitric oxide (NO) or poly-ADP ribose polymerase (PARP-1) activation is sexually dimorphic and that interruption of these molecular death pathways benefits only the male brain. Female neuronal nitric oxide synthase (nNOS) knockout (nNOS−/−) mice exhibited exacerbated histological injury after middle cerebral artery occlusion (MCAO) relative to wild-type (WT) females, unlike the protection observed in male nNOS−/− littermates. Similarly, treatment with the nNOS inhibitor (7-nitroindozole, 25 mg/kg) increased infarction in female C57Bl6 WT mice, but protected male mice. The mechanism for this sexually specific response is not mediated through changes in protein expression of endothelial NOS or inducible NOS, or differences in intraischemic cerebral blood flow. Unlike male PARP-1 knockouts (PARP1−/−), female PARP1−/− littermates sustained grossly increased ischemic damage relative to sex-matched WT mice. Treatment with a PARP inhibitor (PJ-34, 10 mg/kg) resulted in identical results. Loss of PARP-1 resulted in reversal of the neuroprotective activity by the female sex steroid, 17β estradiol. These data suggest that the previously described cell death pathways involving NO and PARP ischemic neurotoxicity may be operant solely in male brain and that the integrity of nNO/PARP-1 signaling is paradoxically protective in the female.
Treatment of spin-coupled metal-centres in pulsed electron–electron double-resonance experiments
Authors: Elsaesser C. , Brecht M. , Bittl R.
Published: February 2005

In applications of ELDOR (electron–electron double-resonance) spectroscopy to metal centres, significant g-anisotropy and spin-coupling within multinuclear clusters have to be considered. We show the difficulties and the advantages arising from these effects.
Hydrogen metabolism in the hyperthermophilic bacterium Aquifex aeolicus
Authors: Guiral M. , Aubert C. , Giudici-Orticoni M.-T.
Published: February 2005

Aquifex aeolicus is a microaerophilic, hydrogen-oxidizing, hyperthermophilic bacterium containing three [NiFe] hydrogenases. Two of these three enzymes (one membrane-bound and one soluble) have been purified and characterized. The Aquifex hydrogenases are thermostable and tolerant to oxygen. A cellular function for the three hydrogenases has been proposed. The two membrane-bound periplasmic hydrogenases may function in energy conservation, whereas the soluble cytoplasmic hydrogenase is probably involved in the CO2 fixation pathway.
Anaerobic regulation of hydrogenase transcription in different bacteria
Authors: Kovács Á.T. , Rákhely G. , Balogh J. , Maróti G. , Fülöp A. , Kovács K.L.
Published: February 2005

Hydrogen metabolism is closely related to other important metabolic and energetic processes of bacterial cells, such as photosynthesis, anaerobic respiration and sulphur metabolism. Even small environmental changes influence these networks through different regulatory systems. The presence or absence of oxygen is one of the most important signals; how the cascades evolved to transmit this signal in different bacteria is summarized. In many instances, hydrogen is released only under anoxic conditions, because of bioenergetic considerations. Most [NiFe] hydrogenases are inactivated by oxygen, but many of them can be re-activated under reducing conditions. In addition to direct inactivation of the hydrogenases, oxygen can also regulate their expression. The global regulatory systems [FNR (fumarate and nitrate reduction regulator), ArcAB (aerobic respiratory control) and RegAB], which respond to alterations in oxygen content and redox conditions of the environment, have an important role in hydrogenase regulation of several bacteria. FNR-like proteins were shown to be important for the regulation of hydrogenases in Escherichia coli, Thiocapsa roseopersicina and Rhizobium leguminosarum, whereas RegA protein modulates the expression of hupSL genes in Rhodobacter capsulatus.
The exceptional photofermentative hydrogen metabolism of the green alga Chlamydomonas reinhardtii
Authors: Hemschemeier A. , Happe T.
Published: February 2005

The photosynthetic green alga Chlamydomonas reinhardtii is capable of performing a complex fermentative metabolism which is related to the mixed acid fermentation of bacteria such as Escherichia coli. The fermentative pattern includes the products formate, ethanol, acetate, glycerol, lactate, carbon dioxide and molecular hydrogen (H2). H2 production is catalysed by an active [Fe]-hydrogenase (HydA) which is coupled with the photosynthetic electron-transport chain. The most important enzyme of the classic fermentation pathway is pyruvate formate-lyase, which is common in bacteria but seldom found in eukaryotes. An interaction between fermentation, photosynthesis and H2 evolution allows the algae to overcome long periods of anaerobiosis. In the absence of sulphur, the cells establish a photofermentative metabolism and accumulate large amounts of H2.
Interacting regulatory networks in the facultative photosynthetic bacterium, Rhodobacter sphaeroides 2.4.1
Authors: Kaplan S. , Eraso J. , Roh J.H.
Published: February 2005

Regulation of photosynthetic membrane synthesis in Rhodobacter sphaeroides 2.4.1 is dependent on the interactions of numerous regulatory elements, with two of the most important being the cbb3 terminal oxidase and the PrrBAC two-component regulatory system. Here, we reveal that the cbb3 terminal oxidase possesses extensive, additional regulatory activities under anaerobic conditions, and that the PrrBAC system is further involved in the regulation of the expression of more than 20% of the R. sphaeroides genome under anaerobic conditions, extending well beyond functions related to redox gene expression.
Approaches to developing biological H2-photoproducing organisms and processes
Authors: Ghirardi M.L. , King P.W. , Posewitz M.C. , Maness P. Ching , Fedorov A. , Kim K. , Cohen J. , Schulten K. , Seibert M.
Published: February 2005

The development of efficient biological systems for the direct photoproduction of H2 gas from water faces several challenges, the more serious of which is the sensitivity of the H2-evolving enzymes (hydrogenases) to O2, an obligatory by-product of photosynthesis. This high sensitivity is common to both FeFe and NiFe hydrogenases, and is caused by O2 binding to their respective metallocatalytic sites. This overview describes approaches to (i) molecular engineering of algal FeFe-hydrogenase to prevent O2 access to its catalytic site; (ii) transform a cyanobacterium with an O2-tolerant bacterial NiFe hydrogenase or (c) partially inactivate algal O2-evolution activity to create physiologically anaerobiosis and induce hydrogenase expression.
Genetics and biotechnology of the H2-uptake [NiFe] hydrogenase from Rhizobium leguminosarum bv. viciae, a legume endosymbiotic bacterium
Authors: Palacios J.M. , Manyani H. , Martínez M. , Ureta A.C. , Brito B. , Báscones E. , Rey L. , Imperial J. , Ruiz-Argüeso T.
Published: February 2005

A limited number of strains belonging to several genera of Rhizobiaceae are capable of expressing a hydrogenase system that allows partial or full recycling of hydrogen evolved by nitrogenase, thus increasing the energy efficiency of the nitrogen fixation process. This review is focused on the genetics and biotechnology of the hydrogenase system from Rhizobium leguminosarum bv. viciae, a frequent inhabitant of European soils capable of establishing symbiotic association with peas, lentils, vetches and other legumes.
Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii
Authors: Posewitz M.C. , King P.W. , Smolinski S.L. , Smith R. Davis , Ginley A.R. , Ghirardi M.L. , Seibert M.
Published: February 2005

The eukaryotic green alga, Chlamydomonas reinhardtii, produces H2 under anaerobic conditions, in a reaction catalysed by an [FeFe]-hydrogenase. To identify genes that influence H2 production in C. reinhardtii, a library of 6000 colonies on agar plates was screened with sensitive chemochromic H2-sensor films for clones defective in H2 production. Two mutants of particular interest were fully characterized. One mutant, hydEF-1, is unable to assemble an active [FeFe]-hydrogenase. This is the first reported C. reinhardtii mutant that is not capable of producing any H2. The second mutant, sta7-10, is not able to accumulate insoluble starch and has significantly lowered H2-photoproduction rates in comparison with the wild-type. In hydEF-1, anaerobiosis induces transcription of the two reported C. reinhardtii hydrogenase genes, HydA1 and HydA2, indicating a normal transcriptional response to anaerobiosis. In contrast, the transcription of both hydrogenase genes in sta7-10 is significantly attenuated.
Common principles in the biosynthesis of diverse enzymes
Authors: Jack R.L. , Dubini A. , Palmer T. , Sargent F.
Published: February 2005

A subset of bacterial periplasmic enzymes are transported from the cytoplasm by the twin-arginine transport apparatus. Such proteins contain distinctive N-terminal signal peptides containing a conserved SRRXFLK ‘twin-arginine’ amino acid motif and often bind complex cofactors before the transport event. It is important that assembly of complex cofactor-containing, and often multi-subunit, enzymes is complete before export. Studies of the unrelated [NiFe] hydrogenase, DMSO reductase and trimethylamine N-oxide reductase systems from Escherichia coli have enabled us to define a chaperone-mediated ‘proofreading’ mechanism involved in co-ordinating assembly and export of twin-arginine transport-dependent enzymes.
The emerging molecular structure of the nitrogen cycle: an introduction to the proceedings of the 10th annual N-cycle meeting
Authors: Butler C.S. , Richardson D.J.
Published: February 2005

Over the last 10 years, during the lifetime of the nitrogen cycle meetings, structural biology, coupled with spectroscopy, has had a major impact of our understanding enzymology of the nitrogen cycle. The three-dimensional structures for many of the key enzymes have now been resolved and have provided a wealth of information regarding the architecture of redox active metal sites, as well as revealing novel structural folds. Coupled with structure-based spectroscopic analysis, this has led to new insight into the reaction mechanisms of the diverse chemical transformations that together cycle nitrogen in the biosphere. An overview of the some of the key developments in field over the last decade is presented.
Chaperones involved in assembly and export of N-oxide reductases
Authors: Hatzixanthis K. , Richardson D.J. , Sargent F.
Published: February 2005

Controlled targeting and transport of redox enzymes to and across the bacterial cytoplasmic membrane is essential for bacterial respiration. A subset of bacterial redox enzymes is exported as folded proteins on the Tat (twin-arginine transport) pathway. Protein export is the point-of-no-return for passenger proteins on the Tat pathway and it is crucial that complex, cofactor-containing enzymes are fully assembled before export is attempted. Using the Escherichia coli trimethylamine N-oxide reductase system as a model, we discuss here the molecular processes governing assembly and export of Tat-dependent enzymes.
The complete denitrification pathway of the symbiotic, nitrogen-fixing bacterium Bradyrhizobium japonicum
Authors: Bedmar E.J. , Robles E.F. , Delgado M.J.
Published: February 2005

Denitrification is an alternative form of respiration in which bacteria sequentially reduce nitrate or nitrite to nitrogen gas by the intermediates nitric oxide and nitrous oxide when oxygen concentrations are limiting. In Bradyrhizobium japonicum, the N2-fixing microsymbiont of soya beans, denitrification depends on the napEDABC, nirK, norCBQD, and nosRZDFYLX gene clusters encoding nitrate-, nitrite-, nitric oxide- and nitrous oxide-reductase respectively. Mutational analysis of the B. japonicum nap genes has demonstrated that the periplasmic nitrate reductase is the only enzyme responsible for nitrate respiration in this bacterium. Regulatory studies using transcriptional lacZ fusions to the nirK, norCBQD and nosRZDFYLX promoter region indicated that microaerobic induction of these promoters is dependent on the fixLJ and fixK2 genes whose products form the FixLJ–FixK2 regulatory cascade. Besides FixK2, another protein, nitrite and nitric oxide respiratory regulator, has been shown to be required for N-oxide regulation of the B. japonicum nirK and norCBQD genes. Thus nitrite and nitric oxide respiratory regulator adds to the FixLJ–FixK2 cascade an additional control level which integrates the N-oxide signal that is critical for maximal induction of the B. japonicum denitrification genes. However, the identity of the signalling molecule and the sensing mechanism remains unknown.
Complexity and diversity in c-type cytochrome biogenesis systems
Authors: Allen J.W.A. , Ginger M.L. , Ferguson S.J.
Published: February 2005

c-type cytochromes contain haem covalently attached to protein by thioether bonds formed post-translationally and requiring a dedicated biogenesis apparatus. Three biogenesis systems, found in different cell types, are well known. Here we discuss emerging evidence for at least one additional system, for unanticipated diversity in the location of the systems and for the co-existence of multiple systems in some cells.
Nitrogen fixation: key genetic regulatory mechanisms
Authors: Martinez-Argudo I. , Little R. , Shearer N. , Johnson P. , Dixon R.
Published: February 2005

The necessity to respond to the level of fixed nitrogen and external oxygen concentrations and to provide sufficient energy for nitrogen fixation imposes common regulatory principles amongst diazotrophs. The NifL–NifA system in Azotobacter vinelandii integrates the signals of redox, fixed-nitrogen and carbon status to regulate nif transcription. Multidomain signalling interactions between NifL and NifA are modulated by redox changes, ligand binding and interaction with the signal-transduction protein GlnK. Under adverse redox conditions (excess oxygen) or when fixed nitrogen is in excess, NifL forms a complex with NifA in which transcriptional activation is prevented. Oxidized NifL forms a binary complex with NifA to inhibit NifA activity. When fixed nitrogen is in excess, the non-covalently modified form of GlnK interacts with NifL to promote the formation of a GlnK–NifL–NifA ternary complex. When the cell re-encounters favourable conditions for nitrogen fixation, it is necessary to deactivate the signals to ensure that the NifL–NifA complex is dissociated so that NifA is free to activate transcription. This is achieved through interactions with 2-oxoglutarate, a key metabolic signal of the carbon status, which binds to the N-terminal GAF (cGMP-specific and stimulated phosphodiesterases, Anabaena adenylate cyclases and Escherichia coliFhlA) domain of NifA.
Plasmid replicons of Rhizobium
Authors: Crossman L.C.
Published: February 2005

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.
Function of the Rhizobium etli CFN42 nirK gene in nitrite metabolism
Authors: Bueno E. , Gómez-Hernández N. , Girard L. , Bedmar E.J. , Delgado M.J.
Published: February 2005

Rhizobium etli CFN42 is not capable of growing anaerobically with nitrate but it grows with nitrite as a terminal electron acceptor. This bacterium contains the nirK gene encoding the copper-containing Nir (nitrite reductase), which is located on the cryptic plasmid pCFN42f. Mutational analysis has demonstrated that a nirK deficient mutant was not capable of growing under nitrite-respiring conditions. Moreover, microaerobic growth of this mutant was inhibited by the presence of nitrite. Nir activity and nitrite uptake were highly diminished in a nirK mutant, compared with the wild-type levels after incubation under anaerobic conditions. Our results suggest that the copper-containing Nir may have both a respiratory and a nitrite-detoxifying role in R. etli.
Complex formation between AmtB and GlnK: an ancestral role in prokaryotic nitrogen control
Authors: Javelle A. , Merrick M.
Published: February 2005

Ammonium transport proteins belonging to the Amt family are ubiquitous in prokaryotes. In Escherichia coli, the AmtB protein and the associated PII signal transduction protein (GlnK) have recently been recognized as an ammonium sensory system that effectively couples the intracellular nitrogen regulation (Ntr) system to external changes in ammonium availability. Given the almost invariant coupling of AmtB and GlnK in bacteria and archaea it seems probable that these two proteins may constitute an ancestral nitrogen-responsive system that has been coupled with a variety of unrelated nitrogen regulatory processes, which are now found in prokaryotes. The multiplicity of PII proteins could therefore be considered to have evolved from an ancestral GlnK-like protein and to have subsequently been adapted to control many other aspects of nitrogen metabolism.