bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosensitizing Properties of Triplet β‐Lapachones in Acetonitrile Solution
Authors: Netto‐Ferreira José Carlos , Lhiaubet‐Vallet Virginie , De Oliveira Bernardes Bauer , Ferreira Aurelio Baird Buarque , Miranda Miguel Ángel 
Published: July 2008

AbstractThe photochemical reactivity of β‐lapachone (1), nor‐β‐lapachone (2) and 1,2‐naphthoquinone (3) towards amino acids and nucleobases or nucleosides has been examined employing the nanosecond laser flash photolysis technique. Excitation (λ = 355 nm) of degassed solutions of 1–3, in acetonitrile, resulted in the formation of their corresponding triplet excited states. These transients were efficiently quenched by l‐tryptophan, l‐tryptophan methyl ester, l‐tyrosine, l‐tyrosine methyl ester and l‐cysteine (kq ≈ 109 L mol−1 s−1). For l‐tryptophan, l‐tyrosine and their methyl esters new transients were formed in the quenching process, which were assigned to the corresponding radical pair resulting from an initial electron transfer from the amino acids or their esters to the excited quinone, followed by a fast proton transfer. No measurable quenching rate constants could be observed in the presence of thymine and thymidine. On the other hand, efficient rate constants were obtained when 1–3 were quenched by 2′‐deoxyguanosine (kq ≈ 109 L mol−1 s−1). The quantum efficiency of singlet oxygen (1O2) formation from 1 to 3 was determined employing time‐resolved near‐IR emission studies upon laser excitation and showed considerably high values in all cases (ΦΔ = 0.6), which are fully in accord with the ππ* character of these triplets in acetonitrile.
Photodegradation of 2‐chloro Substituted Phenothiazines in Alcohols
Authors: García Carmelo , Piñero Luis , Oyola Rolando , Arce Rafael 
Published: July 2008

AbstractThe mechanisms that trigger the phototoxic response to 2‐chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption‐ and emission‐spectroscopy, 1H‐ and 13C‐NMR and GC‐MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce et al. (J. Med. Chem. 22, 202–204) to explain the large difference between the photodestruction quantum yield of 2‐chlorpromazine (ϕ = 0.46) and 2‐chlorphenothiazine (ϕ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10‐substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient.
A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter
Authors: Paris Cecilia , Lhiaubet‐Vallet Virginie , Jiménez Oscar , Trullas Carles , Miranda Miguel Ángel 
Published: July 2008

AbstractNovel sunscreens are required providing active protection in the UVA and UVB regions. On the other hand, there is an increasing concern about the photosafety of UV filters, as some of them are not sufficiently photostable. Avobenzone is one of the most frequently employed sunscreen ingredients, but it has been reported to partially decompose after irradiation. In the present work, photophysical and photochemical studies on a methylated avobenzone‐derivative have shown that the diketo form is responsible for photodegradation. A transient absorption was observed at 380 nm after laser flash photolysis excitation at 308 nm. It was assigned to the triplet excited state of the diketo form, as inferred from quenching by oxygen and β‐carotene. This transient also interacted with key building blocks of biomolecules by triplet–triplet energy transfer (in the case of thymidine) or electron transfer processes (for 2′‐deoxyguanosine, tryptophan and tyrosine). Irradiation of the avobenzone derivative in the presence of a triazine UV‐B filter (E‐35852) diminished the undesirable effects of the compound by an efficient quenching of the triplet excited state. Thus, sunscreen formulations including triplet quenchers could provide effective protection from the potential phototoxic and photoallergic effects derived from poor photostability of avobenzone.
Comparative Analysis of Antibiotic Resistance Characteristics of Gram‐negative Bacteria Isolated from Laying Hens and Eggs in Conventional and Organic Keeping Systems in Bavaria, Germany
Authors: Schwaiger K. , Schmied E.‐M. V. , Bauer J. 
Published: July 2008

SummaryBy investigating the prevalence and resistance characteristics of Gram‐negative bacteria from organic and conventional kept laying hens against 31 (Campylobacter: 29) different antibiotics using the microdilution method, we determined to what extent different keeping systems influence bacterial resistance patterns. For this purpose, samples from 10 organic and 10 conventional flocks in Bavaria (Germany) were investigated four times between January 2004 and April 2005. Altogether, 799 cloacal swabs and 800 eggs (contents and shells) were examined. The bacterial investigation performed with standardized cultural methods showed prevalence for all bacteria groups in about the same order of magnitude in the two different keeping systems: Salmonella spp. 3.5% (organic [org]) versus 1.8% (conventional [con]); Campylobacter spp. 34.8%org versus 29.0%con and E. coli 64.4%org versus 69.0%con. Coliforms (Citrobacter, Enterobacter, Pantoea) were only isolated in single cases. In eggs, generally less bacteria were detected, predominantly Escherichia; Salmonella and Campylobacter were only scarcely isolated. Salmonella enterica ssp. enterica serovar Typhimurium (n = 10) were resistant to up to nine, S. of the serogroup B (n = 4) up to six antibiotics. All tested Salmonella (n = 23) proved to be resistant to spectinomycin. Escherichia coli (n = 257org and 276con) from organic layers showed significant lower resistance rates and higher rates of susceptible isolates to nine agents, namely amoxicillin/clavulanic acid, ampicillin, cefaclor, cefoxitin, cefuroxime, doxycycline, mezlocillin, neomycin and piperacillin. In contrast, only two antibiotics turned out to be more effective in conventional isolates (gentamicin and tobramycin). In the case of Campylobacter jejuni (n = 118org and 99con), statistically significantly better rates were observed for isolates from organic flocks concerning imipenem and amoxicillin/clavulanic acid, whereas fosfomycin was more potent in strains from conventional flocks. Results of this study indicate that both resistance rates and mean minimum inhibitory concentrations of bacteria isolated from organic keeping systems have lower values than those from conventional ones, particularly recognizable for E. coli. Thus, organic livestock farming with its restrictions and additional requirements contributes to further effectiveness of antibiotics.
The Anthrax Vaccine Adsorbed Vaccine Generates Protective Antigen (PA)-Specific CD4
+
T Cells with a Phenotype Distinct from That of Naïve PA T Cells
Authors: Kwok William W. , Yang Junbao , James Eddie , Bui John , Huston Laurie , Wiesen Andrew R. , Roti Michelle 
Published: August 2008

ABSTRACT

Cellular immune responses against protective antigen (PA) of
Bacillus anthracis
in subjects that received the anthrax vaccine adsorbed (AVA) vaccine were examined. Multiple CD4
+
T-cell epitopes within PA were identified by using tetramer-guided epitope mapping. PA-reactive CD4
+
T cells with a CD45RA
−
phenotype were also detected by direct ex vivo staining of peripheral blood mononuclear cells (PBMC) with PA-specific tetramers. Surprisingly, PA-specific T cells were also detected in PBMC of nonvaccinees after a single cycle of in vitro PA stimulation. However, PA-reactive CD4
+
T cells in nonvaccinees occurred at lower frequencies than those in vaccinees. The majority of PA-reactive T cells from nonvaccinees were CD45RA
+
and exhibited a Th0/Th1 cytokine profile. In contrast, phenotyping and cytokine profile analyses of PA-reactive CD4
+
T cells from vaccinees indicated that vaccination leads to commitment of PA-reactive T cells to a Th2 lineage, including generation of PA-specific, pre-Th2 central memory T cells. These results demonstrate that the current AVA vaccine is effective in skewing the development of PA CD4
+
T cells to the Th2 lineage. The data also demonstrated the feasibility of using class II tetramers to analyze CD4
+
cell responses and lineage development after vaccination.
Characterization of Chromosomal Regions Conserved in
Yersinia pseudotuberculosis
and Lost by
Yersinia pestis
Authors: Pouillot Flavie , Fayolle Corinne , Carniel Elisabeth 
Published: August 2008

ABSTRACT

The transformation of the enteropathogenic bacterium
Yersinia pseudotuberculosis
into the plague bacillus,
Yersinia pestis
, has been accompanied by extensive genetic loss. This study focused on chromosomal regions conserved in
Y. pseudotuberculosis
and lost during its transformation into
Y. pestis
. An extensive PCR screening of 78 strains of the two species identified five regions (R1 to R5) and four open reading frames (ORFs;
orf1
to
orf4
) that were conserved in
Y. pseudotuberculosis
and absent from
Y. pestis
. Their conservation in
Y. pseudotuberculosis
suggests a positive selective pressure and a role during the life cycle of this species. Attempts to delete two ORFs (
orf3
and
orf4
) from the chromosome of strain IP32953 were unsuccessful, indicating that they are essential for its viability. The seven remaining loci were individually deleted from the IP32953 chromosome, and the ability of each mutant to grow in vitro and to kill mice upon intragastric infection was evaluated. Four loci (
orf1
, R2, R4, and R5) were not required for optimal growth or virulence of
Y. pseudotuberculosis
. In contrast,
orf2
, encoding a putative pseudouridylate synthase involved in RNA stability, was necessary for the optimal growth of IP32953 at 37°C in a chemically defined medium (M63S). Deletion of R1, a region predicted to encode the methionine salvage pathway, altered the mutant pathogenicity, suggesting that the availability of free methionine is severely restricted in vivo. R3, a region composed mostly of genes of unknown functions, was necessary for both optimal growth of
Y. pseudotuberculosis
at 37°C in M63S and for virulence. Therefore, despite their loss in
Y. pestis
, five of the nine
Y. pseudotuberculosis
-specific chromosomal loci studied play a role in the survival, growth, or virulence of this species.
Toxoplasma gondiiRhoptry Discharge Correlates with Activation of the Early Growth Response 2 Host Cell Transcription Factor
Authors: Phelps Eric D. , Sweeney Kristin R. , Blader Ira J. 
Published: August 2008

ABSTRACTToxoplasma gondiiis a ubiquitous apicomplexan parasite that can cause severe disease in fetuses and immune-compromised patients. Rhoptries, micronemes, and dense granules, which are secretory organelles unique toToxoplasmaand other apicomplexan parasites, play critical roles in parasite growth and virulence. To understand how these organelles modulate infected host cells, we sought to identify host cell transcription factors triggered by their release. Early growth response 2 (EGR2) is a host cell transcription factor that is rapidly upregulated and activated inToxoplasma-infected cells but not in cells infected with the closely related apicomplexan parasiteNeospora caninum. EGR2 upregulation occurred only when live parasites were in direct contact with the host cell and not from exposure to cell extracts that contain dense granule or micronemal proteins. When microneme-mediated attachment was blocked by pretreating parasites with a calcium chelator, EGR2 expression was significantly reduced. In contrast, when host cells were infected with parasites in the presence of cytochalasin D, which allows rhoptry secretion but prevents parasite invasion, EGR2 was activated. Finally, we demonstrate thatToxoplasmaactivation of host p38 mitogen-activated protein kinase is necessary but not sufficient for EGR2 activation. Collectively, these data indicate that EGR2 is specifically upregulated by a parasite-derived secreted factor that is most likely a resident rhoptry protein.
Priority dilemmas in dialysis: the impact of old age
Authors: Halvorsen K , Slettebø Å , Nortvedt P , Pedersen R , Kirkevold M , Nordhaug M , Brinchmann B S 
Published: July 2008

Aim:This study explores priority dilemmas in dialysis treatment and care offered elderly patients within the Norwegian public healthcare system.Background:Inadequate healthcare due to advanced age is frequently reported in Norway. The Norwegian guidelines for healthcare priorities state that age alone is not a relevant criterion. However, chronological age, if it affects the risk or effect of medical treatment, can be a legitimate criterion.Method:A qualitative approach is used. Data were collected through semistructured interviews and analysed through hermeneutical content analysis. The informants were five physicians and four nurses from dialysis wards.Findings:Pressing priority dilemmas centre around decision-making concerning withholding and withdrawal of dialysis treatment. Advanced age is rarely an absolute or sole priority criterion. It seems, however, that advanced age appears to be a more subtle criterion in relation with, for example, comorbidity, functional status and cognitive impairment. Nurses primarily prioritise specialised dialysis care and not comprehensive nursing care. The complex needs of elderly patients are therefore often not always met.Conclusions:Clinical priorities should be made more transparent in order to secure legitimate and fair resource allocation in dialysis treatment and care. Difficult decisions concerning withholding or withdrawal of dialysis ought to be openly discussed within the healthcare team as well as with patients and significant others. The biomedical focus and limitations on comprehensive care during dialysis should be debated.
Patients’ attitudes towards “do not attempt resuscitation” status
Authors: Gorton A J , Jayanthi N V G , Lepping P , Scriven M W 
Published: July 2008

Introduction:The decision of “do not attempt resuscitation” (DNAR) in the event of cardiopulmonary arrest is usually made when the patients are critically ill and cannot make an informed choice. Although, various professional bodies have published guidelines, little is know about the patients’ own views regarding DNAR discussion.Aim:The aim of this study was to determine patients’ attitudes regarding discussing DNAR before they are critically ill.Methods:A prospective study was performed in a general out patients department. A questionnaire was distributed to consecutive outpatients along with an explanatory leaflet in the adult outpatient clinic.Results:364 patients completed the questionnaire (response rate 77%). 90% of respondents wanted all patients to be asked regarding DNAR decision at some point during a hospital admission. The majority would not find a DNAR discussion distressing. Only 10% would find it upsetting, however, 48% of these still wanted a discussion. 37% of respondents wanted to discuss DNAR decisions on admission; 32% in outpatients; 17% at consent for surgery, 14% when they are critically ill. 87% of respondents would not object to their relatives being involved in making decisions about their resuscitation status. However, only 12% of the subjects in the study had been involved in discussing the resuscitation status of a relative and 21% would not be comfortable to discuss a relative’s resuscitation status. Although 33% of patients preferred their resuscitation status to simply be documented within their clinical notes, 77% wanted it to be more easily accessible.Conclusions:This study suggests that contrary to current practice most patients want to discuss their DNAR status prior to becoming critically ill. This includes half of the small number that find it distressing to discuss. Although most patients are comfortable with relatives being involved in discussing DNAR, a significant proportion do not want their relatives to be asked. Furthermore, once a decision has been made, the majority of patients want it to be more accessible than current practice allows.
Early ideas about erratic boulders and glacial phenomena in The Netherlands
Authors: Van Veen Frederik R. 
Published: August 2008

Abstract
The development of ideas about the origin of erratic boulders in the northern Netherlands is reviewed for the period from 1770 to 1907. A Scandinavian origin of these rocks was recognized at an early stage, but the transport mechanism was not understood. Initially, the Biblical Flood was proposed as a geological agent by Horace de Saussure (1740–1799) in 1780. Charles Lyell (1797–1875) developed a theory of climate change and a ‘glacial drift theory’ to account for the movement of large boulders in the Alps, and he introduced the term ‘drift’ in 1840. Several prize contests of the two Dutch Scientific Societies, the Hollandsche Maatschappij der Wetenschappen and the Teyler Genootschap, both at Haarlem, concerned erratics. The competitions of 1827 and 1828 were won by Johann Hausmann (1782–1849) from Göttingen University and Reinhard Bernhardi (1797–1849) from the Forstakademie Hitzacker, respectively. Hausmann assumed that a great freshwater flood, caused by the breakthrough of natural dams in the Scandinavian mountains, swept boulders to the plains of the northern Netherlands. Bernhardi vaguely suggested the possibility of transport by glaciers. The prize for the third contest (1861) was awarded in 1868 to the Swedish geologist Otto Torell (1828–1900). He invoked the land-ice theory, which, as regards The Netherlands, proposed that the boulders had been transported by glaciers descending from the Bothnian Gulf and extending into the northern Netherlands, amongst other areas. However, for reasons unknown, Torell's manuscript was never printed, and he never collected his gold medal and the prize money. At a historic meeting of the Deutsche Geologische Gesellschaft at Berlin in 1875, 7 years after winning the Haarlem contest, Torell managed to convince his audience of the land-ice theory after showing striated rock surfaces at a well-known outcrop at Rüdersdorf near Berlin. Thus, it took about a century from the first speculations in the late eighteenth century about the origin and transport of erratic rocks to about 1880 before the land-ice theory became generally accepted in continental NW Europe.
Griffith Taylor, Ernest Andrews
et al.
: early ideas on the development of the river systems of the Sydney region, eastern Australia, and subsequent ideas on the associated geomorphological problems
Authors: Oldroyd David R. 
Published: August 2008

Abstract

Thomas Griffith Taylor was one of Australia's leading geoscientists in the early twentieth century. He also developed ideas on race and environment at Sydney University, supposing that brachycephalic people had greater intellectual capacity than dolichocephalics, so that Chinese settlement in Australia was desirable. In consequence, Taylor's promotion at Sydney University was blocked. He therefore moved to a chair at Chicago, and thence to Toronto. He retired to Sydney in 1951 and in his old age published a classic study of the landforms of the region:
Sydneyside Scenery
(1958, published by Angus & Robertson, Sydney). This little book, although scientifically somewhat dated even at the time of its publication, summarized Taylor's earlier geomorphological ideas about Sydney and its hinterland. It applied Davisian ideas to the Sydney region, harking back to the work that Taylor and others had done in the early twentieth century. Taylor's ideas about the Sydney region's river patterns are described and their relationship to supposed Earth movements. In particular, Davisian ideas about river capture and antecedent drainage, and the topography of the Blue Mountains, are discussed in relation to the empirical information and theoretical ideas available in the early twentieth century. Taylor's ideas, as described in 1958, seem(ed) plausible, but they were subsequently thrown in doubt or invalidated by consideration of the form of diatremes in the Blue Mountains, by new geological theory, new data about the ages of rocks and minerals and estimates of the timing of Earth movements, closer mapping of structures, etc. The case exemplifies both the explanatory power, and the weaknesses, of Davisian geomorphology. E.C. Andrews preceded Taylor in introducing American geomorphological ideas into Australia and propounded the idea of Late Tertiary–Pleistocene uplift in eastern Australia, which was held responsible for many of the features that Taylor described. Other important contributors were W. G. Woolnough (1876–1958) and T. W. E. David (1858–1934), who taught Woolnough, Andrews and Taylor. A consensual view of the geomorphological and tectonic history of the Sydney region has still not been achieved.
Sir Charles Cotton (1885–1970): international geomorphologist
Authors: Grapes Rodney H. 
Published: August 2008

Abstract

Sir Charles Cotton (1885–1970), a New Zealander by birth, was Professor of Geology at Victoria University of Wellington, New Zealand, between 1921 and 1953. He produced a quartet of well-known textbooks, the most influential being
Geomorphology of New Zealand
first published in 1921, and a remarkable number of pioneering papers on a great variety of subjects in geomorphology. Essentially self-taught, much of Cotton's earlier work followed the ideas of W. M. Davis in terms of an explanatory description of landforms (structure, process, form), but he also emphasized the importance of climate change and tectonic movements in landscape-forming processes. His work was enhanced by the use of block diagrams to demonstrate progressive evolution of landscape features and his simple sketches, in particular, provided a clarity allowing people to see the land around them with new interest and understanding. His studies were never quantitative, and he remained sceptical about illusions of precision and accuracy in the new post-World War II trends and ideas in geomorphology. Cotton's range of interests was wide, but certain themes keep returning; in particular, shore processes and shoreline development and classification, the significance of faulting in all its forms, and the geomorphic history of the area of his Wellington home in New Zealand. Although Cotton's work became well known throughout the scientific world, he did not create a school of geomorphological thought. His international reputation came from his scientific papers and especially his books that captured the interest of generations of university students and citizens from all walks of life. Indeed, the honour of a knighthood in 1959 could well have come 30 years earlier when, at the age of 41, he had already gained such recognition. He made an outstanding contribution to our understanding of the evolution of New Zealand's landforms. Cotton's bibliography is included.