bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Characterization of the
phaEC
Hm
Genes, Required for Biosynthesis of Poly(3-Hydroxybutyrate) in the Extremely Halophilic Archaeon
Haloarcula marismortui
Authors: Han Jing , Lu Qiuhe , Zhou Ligang , Zhou Jian , Xiang Hua
Published: August 2007

Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of
Archaea
have not yet been experimentally investigated yet. In this study, we revealed that
Haloarcula marismortui
was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the
phaE
Hm
and
phaC
Hm
genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaC
Hm
was revealed to be strongly bound with the PHB granules, but PhaE
Hm
seemed not to be. Introduction of either the
phaE
Hm
or
phaC
Hm
gene into
Haloarcula hispanica
, which harbors highly homologous
phaEC
Hh
genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the
phaEC
Hh
genes in
H. hispanica
led to a complete loss of the PHA synthase activity. Complementation with
phaEC
Hm
genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this
phaEC
-deleted haloarchaeon. These results indicated that the
phaEC
genes are required for biosynthesis of PHB and might encode an active PHA synthase in the
Haloarcula
species.
Transcriptome Analysis ofPseudomonas putidaKT2440 Harboring the Completely Sequenced IncP-7 Plasmid pCAR1
Authors: Miyakoshi Masatoshi , Shintani Masaki , Terabayashi Tsuguno , Kai Satoshi , Yamane Hisakazu , Nojiri Hideaki
Published: August 2007

The IncP-7 plasmid pCAR1 ofPseudomonas resinovoransCA10 confers the ability to degrade carbazole upon transfer to the recipient strainP. putidaKT2440. We designed a customized whole-genome oligonucleotide microarray to study the coordinated expression of pCAR1 and the chromosome in the transconjugant strain KT2440(pCAR1). First, the transcriptome of KT2440(pCAR1) during growth with carbazole as the sole carbon source was compared to that during growth with succinate. The carbazole cataboliccarandantoperons were induced, along with the chromosomalcatandpcagenes involved in the catechol branch of the β-ketoadipate pathway. Additionally, the regulatory geneantRencoding the AraC/XylS family transcriptional activator specific forcarandantoperons was upregulated. The characterization of theantRpromoter revealed thatantRis transcribed from an RpoN-dependent promoter, suggesting that the successful expression of the carbazole catabolic operons depends on whether the chromosome contains the specific RpoN-dependent activator. Next, to analyze whether the horizontal transfer of a plasmid alters the transcription network of its host chromosome, we compared the chromosomal transcriptomes of KT2440(pCAR1) and KT2440 under the same growth conditions. Only subtle changes were caused by the transfer of pCAR1, except for the significant induction of the hypothetical gene PP3700, designatedparI, which encodes a putative ParA-like ATPase with an N-terminal Xre-type DNA-binding motif. Further transcriptional analyses showed that theparIpromoter was positively regulated by ParI itself and the pCAR1-encoded protein ParA.
Comparative Genomic Analyses of Seventeen
Streptococcus pneumoniae
Strains: Insights into the Pneumococcal Supragenome
Authors: Hiller N. Luisa , Janto Benjamin , Hogg Justin S. , Boissy Robert , Yu Susan , Powell Evan , Keefe Randy , Ehrlich Nathan E. , Shen Kai , Hayes Jay , Barbadora Karen , Klimke William , Dernovoy Dmitry , Tatusova Tatiana , Parkhill Julian , Bentley Stephen D. , Post J. Christopher , Ehrlich Garth D. , Hu Fen Z.
Published: August 2007

The distributed-genome hypothesis (DGH) states that pathogenic bacteria possess a supragenome that is much larger than the genome of any single bacterium and that these pathogens utilize genetic recombination and a large, noncore set of genes as a means of diversity generation. We sequenced the genomes of eight nasopharyngeal strains of S
treptococcus pneumoniae
isolated from pediatric patients with upper respiratory symptoms and performed quantitative genomic analyses among these and nine publicly available pneumococcal strains. Coding sequences from all strains were grouped into 3,170 orthologous gene clusters, of which 1,454 (46%) were conserved among all 17 strains. The majority of the gene clusters, 1,716 (54%), were not found in all strains. Genic differences per strain pair ranged from 35 to 629 orthologous clusters, with each strain's genome containing between 21 and 32% noncore genes. The distribution of the orthologous clusters per genome for the 17 strains was entered into the finite-supragenome model, which predicted that (i) the
S. pneumoniae
supragenome contains more than 5,000 orthologous clusters and (ii) 99% of the orthologous clusters (∼3,000) that are represented in the
S. pneumoniae
population at frequencies of ≥0.1 can be identified if 33 representative genomes are sequenced. These extensive genic diversity data support the DGH and provide a basis for understanding the great differences in clinical phenotype associated with various pneumococcal strains. When these findings are taken together with previous studies that demonstrated the presence of a supragenome for
Streptococcus agalactiae
and
Haemophilus influenzae
, it appears that the possession of a distributed genome is a common host interaction strategy.
The Hotdog Thioesterase EntH (YbdB) Plays a Role In Vivo in Optimal Enterobactin Biosynthesis by Interacting with the ArCP Domain of EntB
Authors: Leduc Damien , Battesti Aurélia , Bouveret Emmanuelle
Published: August 2007

In response to iron limitation, the siderophore enterobactin is synthesized and secreted by
Escherichia coli
. Its biosynthesis is performed by a series of enzymes encoded by the Ent gene cluster. Among the genes of this cluster,
ybdB
has not been implicated in enterobactin production to date. We demonstrate here an in vivo role for the hotdog protein EntH (YbdB) in the optimal production of enterobactin. Indeed, we showed that EntH is a thioesterase specifically produced under iron limitation conditions. Furthermore, EntH interacts specifically with the aryl carrier protein (ArCP) domain of EntB, a crucial bifunctional enzyme of the enterobactin biosynthesis pathway and a potential target of EntH thioesterase activity. A strain devoid of EntH is impaired for growth under iron limitation associated with the presence of the salicylate inhibitor, correlating with the diminution of enterobactin production under these conditions. Normal growth and enterobactin production are restored upon expression of
entH
in
trans
. Inversely, unnecessary overproduction of EntH provokes a fall of the quantity of siderophore produced under iron starvation conditions. Our findings point to a proofreading role for EntH during biosynthesis of enterobactin in vivo. EntH thioesterase activity could be required for cleaving wrongly charged molecules on the carrier protein EntB. This is the first description of such a role in the optimization of a nonribosomal biosynthesis pathway for a protein of the hotdog superfamily.
Generation of Virulence Factor Variants in
Staphylococcus aureus
Biofilms
Authors: Yarwood Jeremy M. , Paquette Kara M. , Tikh Ilya B. , Volper Esther M. , Greenberg E. Peter
Published: August 2007

Several serious diseases are caused by biofilm-associated
Staphylococcus aureus
. Colonial variants occur in biofilms of other bacterial species, and
S. aureus
variants are frequently isolated from biofilm-associated infections. Thus, we studied the generation of variants with altered expression of virulence factors in
S. aureus
biofilms. We observed that the number of variants found in biofilms, as measured by hemolytic activity, varied for different strains. Further study of hemolytic activity and signaling by the accessory gene regulator (Agr) quorum-sensing system in one
S. aureus
strain revealed three primary biofilm subpopulations: nonhemolytic (Agr deficient), hemolytic (Agr positive), and hyperhemolytic (also Agr positive). The nonhemolytic variant became the numerically dominant subpopulation in the biofilm. The nonhemolytic variant phenotype was stable and heritable, indicating a genetic perturbation, whereas the hyperhemolytic phenotype was unstable, suggesting a phase variation. Transcription profiling revealed that expression of the
agr
locus and many extracellular virulence factors was repressed in the nonhemolytic variant. Expression of the
agr
-activating gene,
sarU
, was also repressed in the nonhemolytic variant, suggesting one potential regulatory pathway responsible for the Agr-deficient phenotype. We suggest that the development of these variants in biofilms may have important clinical implications.
Transcriptomic Analysis of the Sulfate Starvation Response ofPseudomonas aeruginosa
Authors: Tralau Tewes , Vuilleumier Stéphane , Thibault Christelle , Campbell Barry J. , Hart C. Anthony , Kertesz Michael A.
Published: August 2007

Pseudomonas aeruginosais an opportunistic pathogen that causes a number of infections in humans, but is best known for its association with cystic fibrosis. It is able to use a wide range of sulfur compounds as sources of sulfur for growth. Gene expression in response to changes in sulfur supply was studied inP. aeruginosaE601, a cystic fibrosis isolate that displays mucin sulfatase activity, and inP. aeruginosaPAO1. A large family of genes was found to be upregulated by sulfate limitation in both isolates, encoding sulfatases and sulfonatases, transport systems, oxidative stress proteins, and a sulfate-regulated TonB/ExbBD complex. These genes were localized in five distinct islands on the genome and encoded proteins with a significantly reduced content of cysteine and methionine. Growth ofP. aeruginosaE601 with mucin as the sulfur source led not only to a sulfate starvation response but also to induction of genes involved with type III secretion systems.
Regulatory Overlap and Functional Redundancy amongBacillus subtilisExtracytoplasmic Function σ Factors
Authors: Mascher Thorsten , Hachmann Anna-Barbara , Helmann John D.
Published: August 2007

Bacillus subtilis encodes seven extracytoplasmic function (ECF) σ factors that regulate partially overlapping regulons related to cell envelope homeostasis and antibiotic resistance. Here, we investigated their physiological role by constructing a mutant set of single, double, triple, and quadruple ECF σ factor deletions in the undomesticatedB. subtilisstrain NCIB3610. This mutant set was subsequently screened for defects in motility, multicellular differentiation, and sensitivity to more than 200 chemicals by using Phenotype MicroArrays. A quadruple mutant strain, harboring deletions of thesigV,sigY,sigZ, andylaCgene, behaved indistinguishably from the wild-type strain, indicative of either regulatory redundancy or very specific functions of these four ECF σ factors. In contrast, a triple mutant, inactivated for thesigM,sigW, andsigXgenes (but none of the corresponding double mutants), showed a biphasic growth behavior and a complete loss of multicellular differentiation, as judged by both colony formation and the inability to form a pellicle. This triple mutant also displayed a greatly increased sensitivity to detergents and several cell wall antibiotics including β-lactams, polymyxin B, andd-cycloserine. In several cases, these antibiotic-sensitive phenotypes are significantly enhanced in the triple mutant strain relative to strains lacking only one or two σ factors.
Role of Nucleoid-Associated Proteins Hha and H-NS in Expression of
Salmonella enterica
Activators HilD, HilC, and RtsA Required for Cell Invasion
Authors: Olekhnovich Igor N. , Kadner Robert J.
Published: August 2007

The coordinate expression of
Salmonella enterica
invasion genes on
Salmonella
pathogenicity island 1 is under the control of the complex circuits of regulation that involve the AraC/XylS family transcriptional activators HilD, HilC, and RtsA and nucleoid-associated proteins. Single-copy transcription fusions were used to assess the effects of nucleoid-associated proteins Hha and H-NS on
hilD
,
hilC
, and
rtsA
expression. The data show that all three genes,
hilD
,
hilC
, and
rtsA
, were repressed by H-NS and/or Hha. The repression of
rtsA
was the highest among tested genes. The level of
rtsA-lac
was equally elevated in
hns
and
hha
mutants and was further enhanced in the
hns hha
double mutant under low-osmolarity conditions. Electrophoretic mobility shift experiments showed that H-NS and Hha directly bind to the
rtsA
promoter. In addition to the negative control that was exerted by H-NS/Hha under low-osmolarity conditions, the homologous virulence activators HilD, HilC, and RtsA (Hil activators) induced
rtsA-lac
expression in a high-salt medium. A DNase footprinting assay of the
rtsA
promoter revealed one common DNA-binding site for all three Hil activators centered at position −54 relative to the transcriptional start site. In the absence of Hha and H-NS, however, osmoregulation of the
rtsA
promoter was lost, and Hil activators were not required for
rtsA
transcription. These results taken together suggest that the HilD, HilC, and RtsA proteins induce the transcription of the
rtsA
promoter by counteracting H-NS/Hha-mediated repression.
Best practice in macroscopic examination of gastric resections
Authors: Pritchard S A
Published: August 2007

Gastric cancer is one of the most common cancers worldwide, with a frequency that varies greatly across different geographic locations. Over recent decades there has been a marked increase in cancers of the oesophagogastric junction, but gastric cancers have shown a decrease in worldwide incidence. However, they still account for 3–10% of all cancer-related deaths. There has been a steady improvement in prognosis in countries such as Japan, predominantly due to screening programmes and early detection, but this has not been seen in Europe and North America. At present the only curative treatment for gastric cancer is complete surgical resection of the primary tumour, with appropriate lymphadenectomy. High quality histology reports are necessary to provide information on diagnosis, prognosis and future management. They can also be important with regard to research, audit and epidemiological studies. This review examines the evidence-based guidelines for macroscopic examination and block selection for gastric carcinomas, with a brief comment on new surgical techniques.
High-risk human papillomavirus is present in cytologically false-negative smears: an analysis of “normal” smears preceding CIN2/3
Authors: Bulk S , Rozendaal L , Zielinski G D , Berkhof J , Daalmeijer N C Fransen , Snijders P J F , van Kemenade F J , Meijer C J L M
Published: August 2007

Aims:

Cervical screening, currently performed by cervical cytology, depends on the timely detection of malignant lesions for its success. The presence of high-risk human papillomavirus (hrHPV) is associated with an increased risk of subsequent high-grade cervical intra-epithelial neoplasia (CIN2/3) and cervical cancer. The aim of this study was to determine the extent to which hrHPV is present in cervical smears with a high a priori chance of being false negative (ie, in normal smears preceding CIN2/3).

Methods:

Archival specimens of 187 women with CIN2/3 and preceding normal conventional smears were identified retrospectively. Of these specimens, 144 (77%) had adequate cytological samples for further HPV DNA testing.

Results:

Of 144 CIN2/3 lesions, preceding normal smears showed hrHPV positivity in 80% of cases. Of the hrHPV-positive smears, 69% were upgraded cytologically at rescreening compared with 24% of hrHPV-negative smears (p<0.001). Upgrading of smears was not associated with specific hrHPV types (p = 0.217). In over 90% of cases, type concordance in smear and CIN2/3 lesion was demonstrated.

Conclusions:

hrHPV is present in a high proportion of normal archival smears preceding CIN2/3, and false-negative cytology was highly associated with the presence of hrHPV. This supports the current notion that hrHPV testing can be used as a primary cervical screening tool. If so, hrHPV-positive cervical smears should be carefully examined for cytological abnormalities to reduce false-negative cervical cytology.
The correlation of regression in primary melanoma with sentinel lymph node status
Authors: Kaur C , Thomas R J , Desai N , Green M A , Lovell D , Powell B W E M , Cook M G
Published: August 2007

Background:

The significance of regression in primary melanoma has been disputed for many years. Some have suggested regression as a marker for poor prognosis while others have reported a negligible or even a favourable effect, on prognosis.

Aim:

To understand the significance of regression in melanoma and provide further information on whether patients should be subjected to sentinel lymph node biopsy (SLNB) on the basis of regression.

Methods:

146 melanoma cases who had undergone SLNB were included in the study. The histological criteria for offering SLNB were melanoma >1 mm in thickness, Clark’s level IV or those with regression.

Results:

A statistically significant greater proportion of individuals without regression showed sentinel lymph node (SLN) positivity (p = 0.028) compared with those which do show regression. Metastatic disease correlated with growth phase of the primary lesion. All the node positive cases were in the vertical growth phase; none of the cases in radial growth phase and showing regression were associated with nodal metastasis (p = 0.029). 62 cases had melanomas with thickness <1 mm and were in radial growth phase, yet were offered SLNB because of regression. Of these, 44 showed features of regression and all were node negative. The remaining 16 cases of thin melanomas did not show regression; 2 of these had sentinel node metastasis.

Conclusion:

Results suggest that regression is usually a favourable process, particularly in thin melanomas and that metastasis in “thin melanomas showing regression” is real but rare. Variant vertical growth phase, mitoses and other prognostically significant variables may be more important predictors of metastatic potential in thin melanomas.
The role of DXA bone density scans in the diagnosis and treatment of osteoporosis
Authors: Blake Glen M , Fogelman Ignac
Published: August 2007

Dual energy x ray absorptiometry (DXA) scans to measure bone mineral density (BMD) at the spine and hip have an important role in the evaluation of individuals at risk of osteoporosis, and in helping clinicians advise patients about the appropriate use of antifracture treatment. Compared with alternative bone densitometry techniques, hip and spine DXA examinations have a number of advantages that include a consensus that BMD results can be interpreted using the World Health Organization T-score definition of osteoporosis, a proven ability to predict fracture risk, proven effectiveness at targeting antifracture therapies, and the ability to monitor response to treatment. This review discusses the evidence for these and other clinical aspects of DXA scanning, including its role in the new WHO algorithm for treating patients on the basis of their individual fracture risk.
Radical cystectomy: defining the threshold for a surgeon to achieve optimum outcomes
Authors: McCabe John E , Jibawi Abdullah , Javle Pradip M
Published: August 2007

Background

The reorganisation of cancer services in England will result in the creation of specialist high volume cancer surgery centres. Studies have suggested a relationship between increasing surgical volume and improved outcomes in urological pelvic cancer surgery, although to date, they have pre-defined the definition of “high” and “low” volume surgeons.

Aim

To derive the minimum caseload a surgeon requires to achieve optimum outcomes and to examine the effect of the operating centre size upon individual surgeon's outcomes.

Methods

All cystectomies performed for bladder cancer in England over 5 years were analysed from Hospital Episode Statistics (HES) data. Statistical analysis was undertaken to describe the relationship between each surgeon's annual case volume and two outcome measures: in-hospital mortality rate, and hospital stay. The surgeon's outcomes were then analysed with respect to the overall level of activity in their operating centre.

Results

A total of 6308 cystectomies were performed; the mean number of surgeons performing them annually was 327 with an overall mortality rate of 5.53%. A significant inverse correlation (−0.968, p<0.01) was found between case volume and mortality rate. Applying 95% confidence interval estimation, the minimum caseload required to achieve the lowest mortality rate was eight procedures per year. Increasing caseload beyond eight operations per year did not produce a significant reduction in mortality rate.

Conclusion

Analysis of HES data confirms an inverse relationship between surgeon's caseload and mortality for radical cystectomy. A caseload of eight operations per year is associated with the lowest mortality rate.
IKEA in China: Facing Dilemmas in an Emerging Economy
Authors: Wei Li-Qun , Zou Xi
Published: August 2007

This case summarizes the development of IKEA's China operations since the opening of its first store in Shanghai in 1998. Since then, IKEA had added four retail stores in Shanghai, Beijing and Guangzhou. Nevertheless, IKEA still had not been profitable in China. The case aims to identify the underlying factors that influenced IKEA's performance in China. The case starts by summarizing IKEA's history, including its organizational characteristics and the competitive dynamics in the Chinese furniture market. Building on this framework, the strategic challenges of IKEA in China are highlighted. In this regard, the case analyzes the effectiveness of IKEA's distinct furniture concept, pricing strategy, and market positioning in the Chinese furniture market. On the whole, the case aims to provide insights for international business development in the Chinese furniture market.
Motivating Vietnamese Employees and Managers in an American Joint-Venture: What a Challenge!
Authors: Bodolica Virginia , Waxin Marie
Published: August 2007

Paul Fierman, an American expatriate, was the General Director of the Vietnamese subsidiary of Chicago Food and Beverage Company (CFB Co.) in Haiphong. His three-year mandate consisted of preparing and executing, in collaboration with the Asia Pacific Regional Director, a strategy of creating synergy among three Asian subsidiaries, which should allow CFB Co. to conquer the three markets. Six months after his arrival, Paul was facing many problems, including a decrease in the sales of non-alcoholic beverages, the general lack of motivation of management in the subsidiary and unrest among the factory workers who wanted better wages and were threatening to unionize. Now, to save the subsidiary and also his career, Paul needed a rapid action plan to put the subsidiary back on track. He had to present and defend such an action plan during his next meeting with the Asia Pacific Regional Director of CFB Co. This case is useful in examining the challenges in managing in a foreign environment.
STRUCTURE DETECTION FROM A 3D SET OF POINTS WITH ANISOTROPIC ALPHA-SHAPES
Authors: BOUGLEUX SÉBASTIEN , MELKEMI MAHMOUD , ELMOATAZ ABDERRAHIM
Published: August 2007

We present a method to extract polyhedral structures from a three-dimensional set of points, even if these structures are embedded in a perturbed background. The method is based on a family of affine diagrams which is an extension of the Voronoi diagram. These diagrams, namely anisotropic diagrams, are defined by using a parameterized distance whose unit ball is an ellipsoidal one. The parameters, upon which this distance depends, control the elongation and the orientation of the associated ellipsoidal ball. The triangulations, dual to the anisotropic diagrams, have the property to connect points that are not neighbors in the Voronoi diagram. Based on these triangulations, we define a family of three-dimensional anisotropic α-shapes. Unlike Euclidean α-shapes, anisotropic ones allow us to detect linear and planar structures in a given direction. The detection of more general polyhedral structures is obtained by merging several anisotropic α-shapes computed for different orientations.
EFFICIENT COMPUTATION OF LEGENDRE MOMENTS FOR GRAY LEVEL IMAGES
Authors: HOSNY KHALID M.
Published: August 2007

Direct computation of Legendre orthogonal moments requires huge arithmetic operations, which is very time consuming. Many works have described methods for reducing the computations involved in evaluating Legendre moments. Nevertheless, reduction computational complexity is still an open problem and needs more investigation. Existing algorithms mainly focused on binary images and compute Legendre moments using a set of geometric moments. We propose a fast and efficient method for computation of Legendre moments for binary and gray level images. A recurrence formula of one-dimensional Legendre moments will be established using the recursive property of Legendre polynomials; then the method will be extended to calculate the two-dimensional Legendre moments. This method is completely independent on geometric moment. The complexity analysis shows that the proposed method computes Legendre moments more efficiently than the direct method and the other conventional methods.
Devonian
Authors: Bluck B. J. , Cope J. C. W. , Scrutton C. T.
Published: August 2007

The Devonian System was the first pre-Quaternary system to have its base established at an internationally ratified Global Stratotype Section and Point (GSSP). The base of the System was defined at the base of the Monograptus uniformis Biozone at Klonk in Czechoslovakia (McLaren 1977). The upper boundary of the System is fixed by the base of the Carboniferous, which has been recently ratified in a GSSP at La Serre, Herault, France, at a point coincident with the first appearance of the conodont Siphonodella sulcata.

Series. GSSPs have now been designated to define the bases of the Middle and Upper Devonian Series (that of the Lower Devonian being automatically defined by the System boundary).

Stages. Consequent upon the selection of a Czech type section for the basal boundary stratotype of the System, the Germanic stages for the lowest parts of the Devonian were no longer appropriate and Lochkovian and Pragian stages have now been formally defined with stratotypes ratified by the I.U.G.S.

Devon, the nomenclatorial type locality for the Devonian System (Sedgwick & Murchison 1839) is a region of great tectonic complexity and has not provided suitable sections on which to base international correlations. However, the rocks are frequently richly fossilferous and firm correlations can now be established with the intensively studied developments of the Devonian in Belgium and Germany.

Northwards from Devon are found large tracts of the predominantly fluviatile and lacustrine facies which characterizes the Old Red Sandstone. Correlation between the marine Devonian rocks of southwest England and the
Cretaceous
Authors: Hancock J. M. , Rawson P. F.
Published: August 2007

Early Cretaceous

The Cretaceous Period lasted for about 70 million years. During this time there was a major change in the sedimentary history of the area as tectonism died down and deposition started of an extensive blanket of coccolith ooze: the Chalk. The change took place mainly over a brief interval across the Albian/Cenomanian (Lower/Upper Cretaceous) boundary, at about 95 Ma. Until that time crustal extension along the Arctic-North Atlantic megarifts continued to influence the tectonic evolution of northwest Europe (Ziegler 1982, 1988). This tensional régime caused rifting and block faulting, particularly across the Jurassic-Cretaceous boundary (Late Cimmerian movements) and in the mid Aptian (Austrian phase). During the latter phase, sea-floor spreading commenced in the Biscay and central Rockall Rifts. The northern part of the Rockall Rift began to widen too, possibly by crustal stretching rather than sea-floor spreading (Ziegler 1988, p. 75). During the Albian the regional pattern began to change and by the beginning of the Cenomanian rifting had effectively ceased away from the Rockall/Faeroe area.

Most of the Jurassic sedimentary basins continued as depositional areas during the Early Cretaceous, but the more extensive preservation of Lower Cretaceous sediments provides firmer constraints on some of the geographical reconstructions. The marked sea-level fall across the Jurassic-Cretaceous boundary isolated the more southerly basins as areas of non-marine sedimentation, and it was not until the beginning of the Aptian that they became substantially marine.

The extent of emergence of highs in the North Sea area is difficult to assess, especially where
Hazard implications of small-scale edifice instability and sector collapse: a case history from Soufrière Hills Volcano, Montserrat
Authors: Young S. R. , Voight B. , Barclay J. , Herd R. A. , Komorowski J.-C. , Miller A. D. , Sparks R. S. J. , Stewart R. C.
Published: August 2007

During the 1995 to 1998 phase of dome growth at Soufrière Hills Volcano on Montserrat, we documented instability of the steep southern rim of English's Crater, known as Galway's Wall. The horseshoe-shaped English's Crater provided good evidence for previous sector collapses, and assessments undertaken in late 1996 anticipated the possibility of a partial sector collapse and a SW-directed explosion, hazards previously unrecognized on Montserrat.

A change from predominantly endogenous to exogenous growth of the lava dome at the end of 1996 eased the stress on the southern sector. However, rapid dome growth in November and December 1997 led to severe reloading and eventual sector failure at the base of the buried Galway's Wall and in the adjacent hot-spring area. This failure resulted in the debris avalanche and lateral blast of 26 December 1997.

Similar sector collapses at a number of small volcanoes in the Caribbean, as well as worldwide, are evidence that edifice instability develops commonly in dome-forming eruptions. The hazards from a sector collapse and a consequent lateral blast are extreme, and monitoring operations and disaster planning at such volcanoes should focus on these, as well as on the more common hazards of conventional pyroclastic flows associated with dome growth.
Generation of a debris avalanche and violent pyroclastic density current on 26 December (Boxing Day) 1997 at Soufrière Hills Volcano, Montserrat
Authors: Sparks R. S. J. , Barclay J. , Calder E. S. , Herd R. A. , Komorowski J-C. , Luckett R. , Norton G. E. , Ritchie L. J. , Voight B. , Woods A. W.
Published: August 2007

Growth of an andesitic lava dome at Soufriere Hills Volcano, Montserrat, beginning in November 1995, caused instability of a hydrothermally altered flank of the volcano. Catastrophic failure occurred on 26 December 1997, 14 months after the instability was first recognized. Two months before failure a dome lobe had extruded over the unstable area and by 25 December 1997 this had a volume of 113 x 10
6
m
3
. At 03:01 (local time) the flank rocks and some dome talus failed and generated a debris avalanche (volume 46 x 10
6
m
3
). Between 35 and 45 x 10
6
m
3
of the dome then collapsed, generating a violent pyroclastic density current that devastated 10 km
2
of southern Montserrat. The failure of the flank and dome formed two adjacent bowl-shaped collapse depressions. The most intense activity lasted about 11.6 minutes. The hummocky debris avalanche deposit is composed of a mixture of domains of heterolithic breccia. The pyroclastic density current had an estimated peak velocity of 80-90 ms
-1
, and minimum flux of 10
8
kgs
1
. The current was largely erosional on land with most deposition out at sea. Destructive effects included removal of houses, trees and large vehicles, and formation of a scoured surface blackened by a thin (3-4 mm) layer of tar. Two discrete depositional units formed from the pyroclastic density current, each with a lower coarse-grained layer and an upper fine-grained stratified layer. These deposits are overlain by an ashfall layer related to buoyant lofting of the current. Flank failure is attributed to loading of hydrothermally weakened rocks by the dome. The generation of the pyroclastic density current is attributed to failure and explosive disintegration of the dome, involving release and violent expansion of gases initially at high pore pressures.
Sedimentology of deposits from the pyroclastic density current of 26 December 1997 at Soufrière Hills Volcano, Montserrat
Authors: Ritchie L. J. , Cole P. D. , Sparks R. S. J.
Published: August 2007

abstract

At 03:01 (local time) on 26 December 1997, major sector collapse followed by collapse of the andesitic lava dome occurred at Soufrière Hills Volcano, Montserrat. The collapse of the dome involved explosive disintegration and formation of a highly energetic pyroclastic density current (PDC), which was dispersed principally to the SW and devastated an area of 10 km
2
. The deposits of the PDC are divisible into valley-confined and unconfined facies. The latter is characterized by two bipartite units (Units I and II), both of which are composed of a fines-poor layer (layer 1) typically overlain by a finer-grained, fines-rich layer (layer 2). The sequence is interpreted as recording strongly pulsatory (unsteady) flow and is capped by Unit III, an accretionary lapilli-rich fallout layer. There are pronounced variations of lithofacies, thickness, grain size and sedimentary structures related to local topography. The PDC was highly erosive: it sculpted isolated mounds of deposit and heavily scoured the pre-existing substrate. Lithofacies are granulometrically distinct, with median diameter (Mdø) increasing as sorting coefficient (Ãø) decreases. Lithofacies characteristics depend strongly on azimuth over a 70° sector, with major lateral (cross-flow) changes at similar radial distances from the dome. The deposits are similar to those produced in the blast eruptions of Mont Pelée in 1902 and Mount St Helens in 1980. We infer that particle size sorting occurred during explosive expansion of the collapsing lava dome, such that the resulting PDC was initially stratified in both grain size and density. The marked lateral and vertical variations in grain size of the deposits indicate efficient further development of density stratification and grain-size sorting during transport, due to air entrainment and sedimentation.
Tephra fallout in the eruption of Soufrière Hills Volcano, Montserrat
Authors: Bonadonna C. , Mayberry G. C. , Calder E. S. , Sparks R. S. J. , Choux C. , Jackson P. , Lejeune A. M. , Loughlin S. C. , Norton G. E. , Rose W. I. , Ryan G. , Young S. R.
Published: August 2007

Four mechanisms caused tephra fallout at Soufrière Hills Volcano, Montserrat, during the 1995-1999 period: explosive activity (mainly of Vulcanian type), dome collapses, ash-venting and phreatic explosions. The first two mechanisms contributed most of the tephra-fallout deposits (minimum total dense-rock equivalent volume of 23 x 106m3), which vary from massive to layered and represent the amalgamation of the deposits from a large numbers of events. The volume of co-pyroclastic-flow fallout tephra is in the range 4-16° of the associated pyroclastic flow deposits. Dome-collapse fallout tephra is characterized by ash particles generated by fragmentation in the pyroclastic flows and by elutriation of fines. Vulcanian fallout tephra is coarser grained, as it is formed by magma fragmentation in the conduit and by elutriation from the fountain-collapse flows and initial surges. Vulcanian fallout tephra is typically polymodal, whereas dome-collapse fallout tephra is predominantly unimodal. Polymodality is attributed to: overlapping of fallout tephra of different types, premature fallout of fine particles, multiple tephra-fallout sources, and differences in density and grain-size distribution of different components. During both dome collapses and explosions, ash fell as aggregates of various sizes and types. Accretionary lapilli grain size is independent of their diameter and is characterized by multiple subpopulations with a main mode at 5ø. Satellite data indicate that very fine ash can stay in a volcanic cloud for several hours and show that exponential thinning rates observed in proximal areas cannot apply in distal areas.
Observations of low-frequency earthquakes and volcanic tremor at Soufrière Hills Volcano, Montserrat
Authors: Baptie B. , Luckett R. , Neuberg J.
Published: August 2007

The 1995-1999 extrusive phase of the eruption of Soufrière Hills Volcano on Montserrat was dominated by low-frequency volcanic earthquakes (also called long-period and hybrid earthquakes). These earthquakes have distinctive peaked spectra and commonly occur in swarms related to the pressurization of the upper part of the magma conduit. We use data from an array of broadband seismometers to examine spatial and temporal variation in the spectral properties of these earthquakes between January and August 1997. Although spectra are generally stable over long periods of time at a given reference point, we also find evidence for changes in the spectra with time and with event magnitude, which may be attributed to changes in the source. The relative amplitude of spectral peaks varies at different stations around the volcano, leading to the conclusion that the observed wavefield is a combination of both source and propagation effects. We also analyse a number of tremor episodes related both to swarms of low-frequency earthquakes and to volcanic explosions. During certain tremor episodes we observe harmonic spectra, with shifting spectral peaks whose frequencies are the same at all stations. This behaviour can be modelled by repetitive triggering of individual earthquakes, where the trigger frequency changes with time, as well as by time-dependent changes in the acoustic properties of the magma-filled conduit caused by pressurization or depressurization.
Orthology and Functional Conservation in Eukaryotes
Authors: Dolinski Kara , Botstein David
Published: August 2007

In recent years, it has become clear that all of the organisms on the Earth are related to each other in ways that can be documented by molecular sequence comparison. In this review, we focus on the evolutionary relationships among the proteins of the eukaryotes, especially those that allow inference of function from one species to another. Data and illustrations are derived from specific comparison of eight species: Homo sapiens, Mus musculus, Arabidopsis thaliana, Caenorhabditis elegans, Danio rerio, Saccharomyces cerevisiae, and Plasmodium falciparum.
Neuroendocrine Regulation of Feminine Sexual Behavior: Lessons from Rodent Models and Thoughts About Humans
Authors: Blaustein Jeffrey D.
Published: August 2007

Much has been learned concerning the neuroendocrine processes and cellular mechanisms by which steroid hormones influence reproductive behaviors in rodents and other animals. In this review, a short discussion of hormones and feminine sexual behavior in some rodent species is followed by an outline of the main principles that have been learned from these studies. Examples are given of the importance of considering the timing of hormone treatments, dosage of hormone, use of a specific hormone, particular class of hormones, or form of hormone, interactions between hormones, route of administration, peripheral factors that influence hormonal response, and the possible mechanisms of action by which hormones and other factors influence sexual behaviors. Although cellular studies in humans are presently impossible to perform, mechanistic studies in rodents may provide clues about the neuroendocrine mechanisms by which hormones act and interact in the brain to influence behavior in all species, including humans.
Retinoic acid signaling sensitizes hepatic stellate cells to NK cell killing via upregulation of NK cell activating ligand RAE1
Authors: Radaeva Svetlana , Wang Lei , Radaev Sergei , Jeong Won-Il , Park Ogyi , Gao Bin
Published: August 2007

Hepatic stellate cells (HSCs) store 75% of the body's supply of vitamin A (retinol) and play a key role in liver fibrogenesis. During liver injury, HSCs become activated and susceptible to natural killer (NK) cell killing due to increased expression of the NK cell activating ligand retinoic acid early inducible gene 1 (RAE-1). To study the mechanism by which RAE-1 is upregulated in HSCs during activation, an in vitro model of cultured mouse HSCs was employed. RAE-1 was detected at low levels in quiescent HSCs but upregulated in 4- and 7-day cultured HSCs (early activated HSCs), whereas 21-day cultured HSCs (fully activated HSCs) lost RAE-1 expression. High levels of RAE-1 in 4- and 7-day cultured HSCs correlated with their susceptibility to NK cell killing, which was diminished by treatment with RAE-1 neutralizing antibody. Furthermore, retinoic acid (RA) and retinal dehydrogenase (Raldh) levels were upregulated in early activated HSCs compared with quiescent or fully activated HSCs. Blocking RA synthesis by the Raldh inhibitor or blocking RA signaling by the retinoic acid receptor antagonist abolished upregulation of RAE-1 whereas treatment with RA induced RAE-1 expression in HSCs. In conclusion, during activation, HSCs lose retinol, which is either secreted out or oxidized into RA; the latter stimulates RAE-1 expression and sensitizes early activated HSCs to NK cell killing. In contrast, fully activated HSCs become resistant to NK cell killing because of lack of RAE1 expression, leading to chronic liver fibrosis and disease.
Endothelial STAT3 plays a critical role in generalized myocardial proinflammatory and proapoptotic signaling
Authors: Wang Meijing , Zhang Wenjun , Crisostomo Paul , Markel Troy , Meldrum Kirstan K. , Fu Xin Y. , Meldrum Daniel R.
Published: August 2007

Signal transducer and activator of transcription (STAT) 3 is involved in mediating a broad range of biological processes, including cell survival, proliferation, and immune response. Recent evidence has indicated that STAT3 in cardiomyocytes can be activated by ischemic-oxidative stress and exerts cardioprotection in the ischemic heart. There is no information, however, regarding the effect of endothelial cell-derived STAT3 on the myocardial response to ischemiareperfusion (I/R) injury. We hypothesized that the ablation of the STAT3 gene in endothelial cells would worsen postischemic myocardial function by affecting capillary network integrity, suppressing antiapoptotic signaling. Isolated hearts from wild-type and endothelial cell STAT3 knockout (STAT3KO) mice were subjected to 20 min of global ischemia followed by 60 min of reperfusion. Endothelial cell STAT3 deficiency decreased recovery of myocardial function in response to I/R, which was associated with higher levels of LDH release, decreased activation of myocardial STAT3, and elevated p38 MAPK activation in STAT3 endothelial knockout (KO) hearts. In addition, although no significant apoptosis was observed in wild-type and KO hearts, our results showed more expression of myocardial caspase-8 and more apoptosis in the myocardium around the capillary in STAT3KO mice subjected to I/R. Furthermore, endothelial cell STAT3 ablation resulted in increased myocardial expression of IL-6 and suppressor of cytokine signal 3. This study demonstrates that endothelial cell-derived STAT3 plays an important role in postischemic myocardial function.
TNF-α-induced mitochondrial oxidative stress and cardiac dysfunction: restoration by superoxide dismutase mimetic Tempol
Authors: Mariappan Nithya , Soorappan Rajasekaran Namakkal , Haque Masudul , Sriramula Srinivas , Francis Joseph
Published: August 2007

Mitochondria are indispensable for bioenergetics and for the regulation of physiological/signaling events in cellular life. Although TNF-α-induced oxidative stress and mitochondrial dysfunction are evident in several pathophysiological states, the molecular mechanisms coupled with impaired cardiac function and its potential reversal by drugs such as Tempol or apocyanin have not yet been explored. Here, we hypothesize that TNF-α-induced oxidative stress compromises cardiac function by altering the mitochondrial redox state and the membrane permeability transition pore (MPTP) opening, thereby causing mitochondrial dysfunction. We measured the redox states in the cytosol and mitochondria of the heart to understand the mechanisms related to the MPTP and the antioxidant defense system. Our studies demonstrate that TNF-α-induced oxidative stress alters redox homeostasis by impairing the MPTP proteins adenine nucleotide translocator and voltage-dependent anion channel, thereby resulting in the pore opening, causing uncontrolled transport of substances to alter mitochondrial pH, and subsequently leading to dysfunction of mitochondria and attenuated cardiac function. Interestingly, we show that the supplementation of Tempol along with TNF-α restores mitochondrial and cardiac function.
Arterial baroreflex control of muscle sympathetic nerve activity in the transition from rest to steady-state dynamic exercise in humans
Authors: Ogoh Shigehiko , Fisher James P. , Raven Peter B. , Fadel Paul J.
Published: August 2007

We sought to investigate arterial baroreflex (ABR) control of muscle sympathetic nerve activity (MSNA) in the transition from rest to steady-state dynamic exercise. This was accomplished by assessing the relationship between spontaneous variations in diastolic blood pressure (DBP) and MSNA at rest and during the time course of reaching steady-state arm cycling at 50% peak oxygen uptake (V̇o2peak). Specifically, DBP-MSNA relations were examined in eight subjects (25 ± 1 yr) at the start of unloaded arm cycling and then during the initial and a later period of arm cycling once the 50% V̇o2peak work rate was achieved. Heart rate and arterial blood pressure were progressively increased throughout exercise. Although resting MSNA [16 ± 2 burst/min; 181 ± 36 arbitrary units (au) total activity] was unchanged during unloaded cycling, MSNA burst frequency and total activity were significantly elevated during the initial (27 ± 4 burst/min; 367 ± 76 au; P < 0.05) and later (36 ± 7 burst/min; 444 ± 91 au; P < 0.05) periods of exercise. The relationships between DBP and burst incidence, burst strength, and total MSNA were progressively shifted rightward from unloaded to the initial to the later period of 50% V̇o2peak arm cycling without any changes in the slopes of the linear regressions (i.e., ABR sensitivity). Thus a continuous and dynamic resetting of the ABR control of MSNA occurred during the transition from rest to steady-state dynamic exercise. These findings indicate that the ABR control of MSNA was well maintained throughout dynamic exercise in humans, progressively being reset to operate around the exercise-induced elevations in blood pressure and MSNA without any changes in reflex sensitivity.