bluuebunny/crossref_metadata_2025 huggingface dataset:
Antioxidant defences in olive trees during drought stress: changes in activity of some antioxidant enzymes
Authors: Sofo Adriano , Dichio Bartolomeo , Xiloyannis Cristos , Masia Andrea
Published: January 2005

The effects of drought on the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), indoleacetate oxidase (IAAox) and polyphenol oxidase (PPO) were studied in 2-year old Olea europaea L. (cv. ‘Coratina’) plants grown under high temperatures and irradiance levels and gradually subjected to a controlled water deficit. After 20 d without irrigation, mean predawn leaf water potential fell from –0.37 to –5.37 MPa, and decreases in net photosynthesis and transpiration occurred. The activities of SOD, APX, CAT and POD increased in relation to the severity of drought stress in both leaves and roots. In particular, a marked increase in APX activity was found in leaves of plants at severe drought stress. CAT activity increased during severe water deficit conditions in leaves and fine roots. The patterns of POD and IAA oxidase activity ran in parallel and showed increases in relation to the degree of drought. In contrast, PPO activity decreased during the progression of stress in all the tissues studied. The results show that the ability of olive trees to up-regulate the enzymatic antioxidant system might be an important attribute linked to drought tolerance. This could limit cellular damage caused by active oxygen species during water deficit.
Carbon resource sharing and rhizome expansion of Phalaris aquatica plants in grazed pastures
Authors: Cullen Brendan R. , Chapman David F. , Quigley Paul E.
Published: January 2005

The patterns of carbon (C) resource sharing and new rhizome development in phalaris (Phalaris aquatica L. cv. Australian) were examined in grazed pastures in western Victoria. The seasonal pattern of new rhizome growth was similar under the four grazing systems tested. New rhizome production was infrequent but concentrated in winter. The phalaris plants maintained more than 1600 kg DW ha–1 of non-assimilating material beneath the soil surface (0–5 cm). Gaseous 14C was fed into plants in the field to determine if these below ground structures continued to be supported by the C assimilating tillers. The results indicated that the primary tiller does provide C to support the growth of secondary and tertiary tillers derived from its axillary buds. There was some evidence that C was exported from the fed tiller to non-assimilating plant structures. The old reproductive tiller bases (from which the assimilating tillers originate) received some C support, suggesting that this was maintained because it had deep roots attached. C export to older plant parts declined, which may lead to plant fragmentation.
Pest and disease protection conferred by expression of barley β - hordothionin and Nicotiana alata proteinase inhibitor genes in transgenic tobacco
Authors: Charity Julia A. , Hughes Peter , Anderson Marilyn A. , Bittisnich Dennis J. , Whitecross Malcolm , Higgins T. J. V.
Published: January 2005

Proteinase inhibitors and thionins are among the many proteins thought to have a role in plant defence against pests and pathogens. Complementary DNA clones encoding the precursors of a multi-domain proteinase inhibitor from Nicotiana alata Link et Otto (NA-PI) (Mr approximately 43 000) and a β-hordothionin (β-HTH) (Mr approximately 13 000) from barley, were linked to constitutive promoters and subsequently transferred by Agrobacterium-mediated transformation into tobacco. The NA-PI and β-HTH precursor proteins were synthesised and post-translationally processed in transgenic tobacco and accumulated as polypeptides of apparent size Mr approximately 6000 and Mr approximately 8500, respectively. The na-pi and β-hth genes were stably inherited for at least two generations. Transgenic tobacco plants containing the highest amounts of NA-PI and β-HTH were crossed to produce plants containing both genes. Helicoverpa armigera (tobacco budworm) larvae that ingested transgenic tobacco leaves expressing both NA-PI and β-HTH, exhibited higher mortality and slower development relative to larvae fed on non-transgenic tobacco. NA-PI and β-HTH, either alone, or in combination, also conferred protection against the fungal pathogen, Botrytis cinerea (grey mould) and the bacterial pathogen, Pseudomonas solanacearum (bacterial wilt). The effect of the two proteins depended upon the organism tested and the contribution of each gene to the protective effects was not necessarily equal. The genetic engineering of plants with proteinase inhibitors or thionins, therefore, has potential for improving crop productivity by simultaneously increasing resistance to both pests and pathogens.
A mutant of Chlamydomonas reinhardtii that cannot acclimate to low CO2 conditions has an insertion in the Hdh1 gene
Authors: Adams James E. , Colombo Sergio L. , Mason Catherine B. , Ynalvez Ruby A. , Tural Baran , Moroney James V.
Published: January 2005

Photosynthetic microorganisms must acclimate to environmental conditions, such as low CO2 environments or high light intensities, which may lead to photo-oxidative stress. In an effort to understand how photosynthetic microorganisms acclimate to these conditions, Chlamydomonas reinhardtii was transformed using the BleR cassette, selected for Zeocin resistance and screened for colonies that showed poor growth at low CO2 levels. One of the insertional mutants obtained, named slc-230, was shown to have a BleR insert in the first exon of Hdh1, a novel, single copy gene. The predicted Hdh1 gene product has similarity to bacterial haloacid dehalogenase-like proteins, a protein family that includes phosphatases and epoxide hydrolases. In addition, Hdh1 is predicted to be localised to the chloroplast or mitochondria in C. reinhardtii. It was found that a genomic copy of wild type Hdh1 can complement slc-230. Physiological studies were conducted to determine the effects of the altered expression of Hdh1 in slc-230. slc-230 grows slowly autotrophically in low CO2, exhibits a lower affinity for inorganic carbon, a decreasing photosynthetic rate over time and a lower content of chlorophylls and quenching xanthophylls than wild type cells. Some possible roles of Hdh1 in the acclimation to low CO2 conditions are discussed.
Plant defence responses: what have we learnt from Arabidopsis?
Authors: Thatcher Louise F. , Anderson Jonathan P. , Singh Karam B.
Published: January 2005

To overcome the attack of invading pathogens, a plant’s defence system relies on preformed and induced responses. The induced responses are activated following detection of a pathogen, with the subsequent transmission of signals and orchestrated cellular events aimed at eliminating the pathogen and preventing its spread. Numerous studies are proving that the activated signalling pathways are not simply linear, but rather, form complex networks where considerable cross talk takes place. This review covers the recent application of powerful genetic and genomic approaches to identify key defence signalling pathways in the model plant Arabidopsis thaliana (L.) Heynh. The identification of key regulatory components of these pathways may offer new approaches to increase the defence capabilities of crop plants.
Plant defence responses: conservation between models and crops
Authors: Anderson Jonathan P. , Thatcher Louise F. , Singh Karam B.
Published: January 2005

Diseases of plants are a major problem for agriculture world wide. Understanding the mechanisms employed by plants to defend themselves against pathogens may lead to novel strategies to enhance disease resistance in crop plants. Much of the research in this area has been conducted with Arabidopsis as a model system, and this review focuses on how relevant the knowledge generated from this model system will be for increasing resistance in crop plants. In addition, the progress made using other model plant species is discussed. While there appears to be substantial similarity between the defence responses of Arabidopsis and other plants, there are also areas where significant differences are evident. For this reason it is also necessary to increase our understanding of the specific aspects of the defence response that cannot be studied using Arabidopsis as a model.
Chromatin remodeling by DNA bending, not twisting
Authors: Lorch Yahli , Davis Barbara , Kornberg Roger D.
Published: January 2005

Single-stranded regions (gaps) in nucleosomal DNA interfere with action of the RSC chromatin-remodeling complex, monitored by exposure of restriction endonuclease cutting sites. Single-strand breaks (nicks) in the DNA, by contrast, have no effect. Gaps on one side of the cutting site are inhibitory, but gaps on the other side are not. A gap >100 bp from the cutting site is as effective as a gap <20 bp from the site. These findings suggest a remodeling process involving bending, but not twisting, of the DNA and further point to the propagation of a bent region (loop or bulge) from one end of the nucleosome to the other.
Identification of the Wnt signaling activator leucine-rich repeat in Flightless interaction protein 2 by a genome-wide functional analysis
Authors: Liu Jun , Bang Anne G. , Kintner Chris , Orth Anthony P. , Chanda Sumit K. , Ding Sheng , Schultz Peter G.
Published: January 2005

The Wnt signaling pathway acts ubiquitously in metazoans to control various aspects of embryonic development. Wnt ligands bind their receptors Frizzled and low-density lipoprotein receptor-related protein 5/6 and function through Disheveled (Dvl), Axin, adenomatous polyposis coli, glycogen synthase kinase 3β, and casein kinase (CK) 1 to stabilize β-catenin and induce lymphocyte enhancer-binding factor (LEF)/T cell factor (TCF)-dependent transcriptional activities. To identify previously unrecognized Wnt signaling modulators, a genome-wide functional screen was performed using large-scale arrayed cDNA collections. From this screen, both known components and previously uncharacterized regulators of this pathway were identified, including β-catenin, Dvl1, Dvl3, Fbxw-1, Cul1, CK1ε, CK1δ, and γ-catenin. In particular, a previously unrecognized activator, LRRFIP2 (leucine-rich repeat in Flightless interaction protein 2), was found that interacts with Dvl to increase the cellular levels of β-catenin and activate β-catenin/LEF/TCF-dependent transcriptional activity. The function of LRRFIP2 is blocked when a dominant negative Dvl (Xdd1) is coexpressed. Expression of LRRFIP2 in
Xenopus
embryos induced double axis formation and Wnt target gene expression; a dominant negative form of LRRFIP2 suppresses ectopic Wnt signaling in
Xenopus
embryos and partially inhibits endogenous dorsal axis formation. These data suggest that LRRFIP2 plays an important role in transducing Wnt signals.
Strategic interactions in multi-institutional epidemics of antibiotic resistance
Authors: Smith David L. , Levin Simon A. , Laxminarayan Ramanan
Published: January 2005

The increasing frequency of antibiotic resistance in hospital-acquired infections is a major public health concern that has both biological and economic causes. Here we develop conceptual mathematical models that couple the economic incentives and population biology of hospital infection control (HIC). We show that the optimal investment by a hospital for HIC changes with the proportion of patients already colonized with antibiotic-resistant bacteria (ARB) at the time of admission. As that proportion increases, the optimal behavior of a hospital is to increase spending to control ARB with low transmissibility and decrease spending on those with high transmissibility. In some cases, the global optimum investment in HIC can shift discontinuously from one that contains transmission to a do-nothing policy once the proportion already colonized at the time of admission becomes too great. We also show that investments in HIC are determined by a strategic game when several hospitals share patients. Hospitals acting selfishly and rationally will free-ride on the investments of other hospitals, and the level of free-riding should increase with the number of other hospitals in the area. Thus, in areas with many hospitals, the rational strategy for each hospital is to spend less than in areas with few hospitals. Thus, we predict that transmission rates and the prevalence of ARB should be higher in urban hospitals, for instance, compared with rural hospitals. We conclude that regional coordination and planning for HIC is an essential element of public health planning for hospital-acquired infections.
Down-regulation of myasthenogenic T cell responses by a dual altered peptide ligand via CD4+CD25+-regulated events leading to apoptosis
Authors: Ben-David Hava , Sela Michael , Mozes Edna
Published: January 2005

The myasthenogenic peptides p195–212 and p259–271 are sequences of the human acetylcholine receptor and were shown to induce myasthenia gravis-associated immune responses in mice. A dual altered peptide ligand (APL) composed of the two APLs of the myasthenogenic peptides inhibited,in vitroandin vivo, those responses. The aims of this study were to elucidate the events that follow thein vivotreatment with the dual APL and to characterize the cell population that is induced by the latter. We demonstrate here that s.c. administration of the dual APL up-regulates CD4+CD25+regulatory T cells that are characterized by up-regulated expression of cytotoxic T lymphocyte-associated antigen 4, intracellular and membranal TGF-β, and Foxp3. Administration of the dual APL to mice concomitant with the immunization with either of the myasthenogenic peptides resulted also in the up-regulation of c-Jun-NH2-terminal kinase activity and of Fas signaling pathway molecules as determined by measuring Fas, Fas ligand, and caspase 8. Thus, our results suggest that the suppression of myasthenia gravis-associated T cell responses exerted by the dual APL is mediated by the CD4+CD25+immunoregulatory T cell function via TGF-β or cytotoxic T lymphocyte-associated antigen 4, which further stimulate a cascade of events that up-regulates apoptosis.
Structure of the kainate receptor subunit GluR6 agonist-binding domain complexed with domoic acid
Authors: Nanao Max H. , Green Tim , Stern-Bach Yael , Heinemann Stephen F. , Choe Senyon
Published: January 2005

We report the crystal structure of the glycosylated ligand-binding (S1S2) domain of the kainate receptor subunit GluR6, in complex with the agonist domoate. The structure shows the expected overall homology with AMPA and NMDA receptor subunit structures but reveals an unexpected binding mode for the side chain of domoate, in which contact is made to the larger lobe only (lobe I). In common with the AMPA receptor subunit GluR2, the GluR6 S1S2 domain associates as a dimer, with many of the interdimer contacts being conserved. Subtle differences in these contacts provide a structural explanation for why GluR2 L483Y and GluR3 L507Y are nondesensitizing, but GluR6, which has a tyrosine at that site, is not. The structure incorporates native glycosylation, which has not previously been described for ionotropic glutamate receptors. The position of the sugars near the subunit interface rules out their direct involvement in subunit association but leaves open the possibility of indirect modulation. Finally, we observed several tetrameric assemblies that satisfy topological constraints with respect to connection to the receptor pore, and which are therefore candidates for the native quaternary structure.
Identification of target genes in breast cancer cells directly regulated by the SRC-3/AIB1 coactivator
Authors: Labhart Paul , Karmakar Sudipan , Salicru Eleni M. , Egan Brian S. , Alexiadis Vassilios , O'Malley Bert W. , Smith Carolyn L.
Published: January 2005

Steroid receptor coactivator-3 (SRC-3/AIB1) is a coactivator for nuclear receptors and other transcription factors and an oncogene that contributes to growth regulation and development of mammary and other tumor types. Because of its biological functions, it is important to identify genes regulated by SRC-3. However, because coactivators do not bind DNA directly, extensive work is required to determine whether genes identified by RNA profiling approaches are direct or indirect targets. Here, we report the use of chromatin immunoprecipitation (ChIP)-based assays that involve genomic mapping and computational analyses of immunoprecipitated DNA to identify SRC-3-binding target genes in estradiol (E2)-treated MCF-7 breast cancer cells. We identified 18 SRC-3 genomic binding sites and demonstrated estrogen receptor-α (ERα) binding to all of them. Both E2-dependent and -independent SRC-3/ERα-binding sites were identified. RNA polymerase II ChIP assays were used to determine the correlation between SRC-3 and ERα binding and recruitment of the transcriptional machinery. These assays, in conjunction with analyses of RNA obtained from E2-treated cells, lead to the identification of SRC-3/ERα-associated genes. The ability of SRC family coactivators to regulate the expression of one of these genes, PARD6B/Par6, was confirmed by using cells individually depleted of SRC-1, SRC-2, or SRC-3 by small interfering RNA. The method described herein can be used to identify genes regulated by non-DNA-binding factors, such as other coactivators or corepressors, as well as DNA-binding transcription factors, and provides information on their binding location that can accelerate further gene characterization.
Thalamic Ca
v
3.1 T-type Ca
2
+ channel plays a crucial role in stabilizing sleep
Authors: Anderson Matthew P. , Mochizuki Takatoshi , Xie Jinghui , Fischler Walter , Manger Jules P. , Talley Edmund M. , Scammell Thomas E. , Tonegawa Susumu
Published: January 2005

It has long been suspected that sensory signal transmission is inhibited in the mammalian brain during sleep. We hypothesized that Ca
v
3.1 T-type Ca
2+
channel currents inhibit thalamic sensory transmission to promote sleep. We found that T-type Ca
2+
channel activation caused prolonged inhibition (>9 s) of action-potential firing in thalamic projection neurons of WT but not Ca
v
3.1 knockout mice. Inhibition occurred with synaptic transmission blocked and required an increase of intracellular Ca
2+
. Furthermore, focal deletion of the gene encoding Ca
v
3.1 from the rostral–midline thalamus by using Cre/
loxP
recombination led to frequent and prolonged arousal, which fragmented and reduced sleep. Interestingly, sleep was not disturbed when Ca
v
3.1 was deleted from cortical pyramidal neurons. These findings support the hypothesis that thalamic T-type Ca
2+
channels are required to block transmission of arousal signals through the thalamus and to stabilize sleep.
Biomarkers in nutritional epidemiology
Authors: Bingham Sheila A
Published: January 2005

Objective:

To illustrate biomarkers of diet that can be used to validate estimates of dietary intake in the study of gene–environment interactions in complex diseases.

Design:

Prospective cohort studies, studies of biomarkers where diet is carefully controlled.

Setting:

Free–living individuals, volunteers in metabolic suites.

Subjects:

Male and female human volunteers.

Results:

Recent studies using biomarkers have demonstrated substantial differences in the extent of measurement error from those derived by comparison with other methods of dietary assessment. The interaction between nutritional and genetic factors has so far largely gone uninvestigated, but can be studied in epidemiological trials that include collections of biological material. Large sample sizes are required to study interactions, and these are made larger in the presence of measurement errors.

Conclusions:

Diet is of key importance in affecting the risk of most chronic diseases in man. Nutritional epidemiology provides the only direct approach to the quantification of risks. The introduction of biomarkers to calibrate the measurement error in dietary reports, and as additional measures of exposure, is a significant development in the effort to improve estimates of the magnitude of the contribution of diet in affecting individual disease risk within populations. The extent of measurement error has important implications for correction for regression dilution and for sample size. The collection of biological samples to improve and validate estimates of exposure, enhance the pursuit of scientific hypotheses, and enable gene–nutrient interactions to be studied, should become the routine in nutritional epidemiology.
Measurement of household food security in the USA and other industrialised countries
Authors: Radimer Kathy L , Radimer Kathy L
Published: January 2005

Abstract Objective: To describe the history and current status of household food security measurement.

Conclusions:

In the 1980s evidence of rising levels of hunger was a concern for many, but disputed by some, Americans. Acknowledgement and quantification of hunger was hindered by the lack of an accepted definition and measure of hunger. Qualitative research at Cornell provided a conceptual framework, description, definition and survey items for hunger. The Community Childhood Hunger Identification Project developed an instrument used in numerous communities. Based upon these initiatives, widely accepted definitions of hunger and food insecurity, and the US Household Food Security Module for its measurement, now exist. The module classifies households as food-secure, or food-insecure without hunger or with moderate or severe hunger, and contains household-, adult- and child-referent items. Its inclusion in the Current Population Survey (CPS) since 1995 has yielded annual estimates of food insecurity. A six-item short form of the module, for surveys with severe time constraints, classifies households only as food-secure or food-insecure without or with hunger and contains no child-specific items. Surveys using the 18-item or short-form module can compare results with published national data from the CPS. Information about the module is available at http://www.ers.usda.gov/briefing/foodsecurity and http://www.fns.usda/fsec. Current research on food security measurement includes measurement of individual food insecurity and hunger, module performance regarding hunger duration and frequency, performance of the module in population subgroups, and the effect of translations on module meaning and performance. National surveys in Canada, New Zealand and Australia also have measured food security.
Modelling Studies on a 100 mm Water‐Injection Cyclone
Authors: Bhaskar K. Udaya , Govindarajan B. , Barnwal J. P. , Rao K. K. , Rao T. C.
Published: January 2005

Test work on a 100 mm water‐injection cyclone was carried out using a ground lead‐zinc ore. Experiments were conducted varying the vortex finder diameter, spigot diameter, feed inlet pressure and injection water rate. The effect of variables on the performance of the water‐injection cyclone in terms of slurry throughput and corrected cut‐size are presented. A set of equations have been developed for predicting the performance of a water‐injection cyclone. Further, the reduced efficiency curve was quantified to predict the size distribution of water‐injection cyclone products.
Rapid Characterization of Magnetic Separator Feed Stocks in Titanium Minerals Processing
Authors: Cavanough G. , Holtham P. N.
Published: January 2005

Magnetic separation is widely used in the processing of titanium minerals. The expected mineral recoveries are assessed by performing laboratory magnetic separations of representative samples to determine the distribution of magnetic components. This is an inherently slow process performed on relatively small samples. This paper describes the development of an inductance based device to rapidly determine the mass distribution of the magnetic properties of a titanium mineral sample. The system is best described as an hourglass with mineral flowing from a hopper through a small inductance coil. The impedance of the coil is proportional to the mean magnetic susceptibility of the number of particles within the coil. An algorithm has been developed to determine the percentage of the feed material at each level of magnetic susceptibility from this measurement. The results are identical to those determined using a laboratory magnetic separation, and are obtained in a fraction of the time. Accuracy of the device has been proven by simulation and by testing of plant samples and comparing the results using the new system with measurements made using a magnetic separator.
Similarity Criteria for Processes of Gravitational Classification
Authors: Barsky E. , Barsky M.
Published: January 2005

Similarity criteria for processes such as gravitational separation of bulk materials are understood as relationships that make it possible to obtain universal curves of separation. For turbulent separation regimes, such criteria were determined earlier [E. Barsky and M. Barsky, Master Curve of Separation Processes. Phys. Sep. Sci. Engin., 13 (2004), 1–13; M.D. Barsky, Powder Fractionation, Moscow, Nedra, 1980 (in Russian)]. In the present article, on the basis of cascade and structural model, similarity criteria are developed, which make it possible to obtain universal curves of separation in all regimes of the motion of the medium. Their applicability is demonstrated on concrete experimental data.
SLon Magnetic Separators Applied in the Ilmenite Processing Industry
Authors: Dahe Xiong
Published: January 2005

SLon vertical ring pulsating high gradient magnetic separators possess the advantages of a large beneficial ratio, high processing efficiency, strong adaptability, high resistance of the magnetic matrix to clogging, and high equipment availability. In recent years, these separators have been successfully applied to the beneficiation of ilmenite ores at the Panzhihua Ilmenite concentrator, and several other ilmenite processing plants, promoting the rapid development of the ilmenite industry in China.
Conditions Providing Optimum Separation
Authors: Barsky Eugene
Published: January 2005

It is generally accepted in the field of powder technology that the most objective quality criterion for the optimization of separation is the Hancock criterion. In this article, use an analytical procedure to show disadvantages of this criterion. I also apply the same analysis to show the objectivity of the entropy criterion for the optimization of separation processes. A simple objective relationship for the optimization of separation processes of pourable materials is derived on the basis of the entropy criterion.
Determinants of the Endosomal Localization of Sorting Nexin 1
Authors: Zhong Qi , Watson Martin J. , Lazar Cheri S. , Hounslow Andrea M. , Waltho Jonathan P. , Gill Gordon N.
Published: January 2005

The sorting nexin (SNX) family of proteins is characterized by sequence-related phox homology (PX) domains. A minority of PX domains bind with high affinity to phosphatidylinositol 3-phosphate [PI(3)P], whereas the majority of PX domains exhibit low affinity that is insufficient to target them to vesicles. SNX1 is located on endosomes, but its low affinity PX domain fails to localize in vivo. The NMR structure of the PX domain of SNX1 reveals an overall fold that is similar to high-affinity PX domains. However, the phosphatidylinositol (PI) binding pocket of the SNX1 PX domain is incomplete; regions of the pocket that are well defined in high-affinity PX domains are highly mobile in SNX1. Some of this mobility is lost upon binding PI(3)P. The C-terminal domain of SNX1 is a long helical dimer that localizes to vesicles but not to the early endosome antigen-1–containing vesicles where endogenous SNX1 resides. Thus, the obligate dimerization of SNX1 that is driven by the C-terminal domain creates a high-affinity PI binding species that properly targets the holo protein to endosomes.
Rab8 Regulates the Actin-based Movement of Melanosomes
Authors: Chabrillat Marion L. , Wilhelm Claire , Wasmeier Christina , Sviderskaya Elena V. , Louvard Daniel , Coudrier Evelyne
Published: January 2005

Rab GTPases have been implicated in the regulation of specific microtubule- and actin-based motor proteins. We devised an in vitro motility assay reconstituting the movement of melanosomes on actin bundles in the presence of ATP to investigate the role of Rab proteins in the actin-dependent movement of melanosomes. Using this assay, we confirmed that Rab27 is required for the actin-dependent movement of melanosomes, and we showed that a second Rab protein, Rab8, also regulates this movement. Rab8 was partially associated with mature melanosomes. Expression of Rab8Q67L perturbed the cellular distribution and increased the frequency of microtubule-independent movement of melanosomes in vivo. Furthermore, anti-Rab8 antibodies decreased the number of melanosomes moving in vitro on actin bundles, whereas melanosomes isolated from cells expressing Rab8Q67L exhibited 70% more movements than wild-type melanosomes. Together, our observations suggest that Rab8 is involved in regulating the actin-dependent movement of melanosomes.
The G Protein-coupled Receptor Gpr1 and the Gα Protein Gpa2 Act through the cAMP-Protein Kinase A Pathway to Induce Morphogenesis inCandida albicans
Authors: Maidan Mykola M. , De Rop Larissa , Serneels Joke , Exler Simone , Rupp Steffen , Tournu Hélène , Thevelein Johan M. , Van Dijck Patrick
Published: January 2005

We investigated the role in cell morphogenesis and pathogenicity of the Candida albicans GPR1 gene, encoding the G protein-coupled receptor Gpr1. Deletion of C. albicans GPR1 has only minor effects in liquid hypha-inducing media but results in strong defects in the yeast-to-hypha transition on solid hypha-inducing media. Addition of cAMP, expression of a constitutively active allele of the Gα protein Gpa2 or of the catalytic protein kinase A subunit TPK1 restores the wild-type phenotype of the CaGPR1-deleted strain. Overexpression of HST7, encoding a component of the mitogen-activated protein kinase pathway, does not suppress the defect in filamentation. These results indicate that CaGpr1 functions upstream in the cAMP–protein kinase A (PKA) pathway. We also show that, in the presence of glucose, CaGpr1 is important for amino acid-induced transition from yeast to hyphal cells. Finally, as opposed to previous reports, we show that CaGpa2 acts downstream of CaGpr1 as activator of the cAMP–PKA pathway but that deletion of neither CaGpr1 nor CaGpa2 affects glucose-induced cAMP signaling. In contrast, the latter is abolished in strains lacking CaCdc25 or CaRas1, suggesting that the CaCdc25-CaRas1 rather than the CaGpr1-CaGpa2 module mediates glucose-induced cAMP signaling in C. albicans.
Transcutaneous penetration of toluene in rat skin a microdialysis study
Authors: Klede Monika , Schmitz Harald , Göen Thomas , Fartasch Manigé , Drexler Hans , Schmelz Martin
Published: January 2005

Abstract:  Percutaneous absorption of lipophilic substances has major implications for therapeutical use or toxicological effects. We, therefore, using dermal microdialysis, measured local toluene concentrations and assessed the effects of duration of exposure, skin barrier disruption and the use of skin‐care products.

Three microdialysis membranes (3000 kDa) were inserted intradermally at a length of 2 cm in the abdominal skin of 82 anaesthetized male Wistar rats. They were perfused with albumin solution (5%) at 10 µl/min. A skin area of 1.5 × 0.6 cm above the membranes was exposed to toluene (100%, 200 µl) for 15 or 240 min. Dialysate was sampled at 20‐min intervals. Using GC‐FPD (gas charomotography flame photometric detector), it was analysed for toluene. In addition, the effects of tape stripping and pretreatment with topical products were assessed. In each of the 12 permutations of exposure time, pretreatments and tape stripping, five to eight animals were investigated.

Maximum toluene concentrations were reached at 60 min after exposure (3.07 ± 0.40 µg/ml, 15 min; 5.38 ± 0.92 µg/ml, 240 min). In 15‐min exposure experiments, dermal toluene concentrations decreased slowly to reach baseline values after 240 min. After 240‐min exposure, a plateau of approximately 6 µg/ml was reached after 60 min. Neither tape stripping nor the pretreatment with barrier cream induced a significant change on dermal toluene concentrations.

The slow kinetics of toluene penetration results in a steep concentration gradient in the skin with very‐high local toluene concentrations and a delayed wash out, which might be relevant not only toxicologically, but also therapeutically.
Specific interleukin‐1 gene polymorphisms in Turkish patients with Behçet's disease
Authors: Coskun Mesut , Bacanli Ali , Sallakci Nilgun , Alpsoy Erkan , Yavuzer Ugur , Yegin Olcay
Published: January 2005

Abstract:  Genetic factors that predispose individuals to Behçet's disease (BD) are considered to play important roles in the development of the disease. The pro‐inflammatory cytokine interleukin‐1 (IL‐1) has been implicated in the pathogenesis of BD. Our aim was to determine a possible association of specific polymorphisms of IL‐1α, IL‐1β, and IL‐1 receptor antagonist genes with susceptibility for BD. We genotyped 72 patients with BD and 163 healthy controls for IL‐1α−889, IL‐1β−511, and +3953 (nt5887) single‐nucleotide polymorphisms besides IL‐1 receptor antagonist variable number of tandem repeat polymorphism (for five different alleles). Comparison of the IL‐1β+3953 T allele and TT genotype frequencies showed a significant difference between patients with BD and controls (54.2 vs. 40.5%, OR = 1.74, P = 0.024, and 40.3 vs. 19.6%, OR = 2.76, P = 0.009, respectively). However, no difference was observed in the genotype or allele frequencies of IL‐1α−889, IL‐1β−511, and IL‐1 receptor antagonist between the patients with BD and the controls. Our results indicate that susceptibility to BD is increased in individuals carrying the IL‐1β+3953 T allele and TT genotype.
Cellular and molecular mechanisms of bleomycin‐induced murine scleroderma: current update and future perspective
Authors: Yamamoto Toshiyuki , Nishioka Kiyoshi
Published: January 2005

Abstract:  Scleroderma is a fibrotic condition characterized by immunologic abnormalities, vascular injury and increased accumulation of matrix proteins in the skin. Although the aetiology of scleroderma is not fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts, via a number of mediators. Cytokines, chemokines and growth factors secreted by inflammatory cells and mesenchymal cells (fibroblasts and myofibroblasts) play an important role in the fibrotic process of scleroderma. Recently, we established a murine model of scleroderma by repeated local injections of bleomycin. Dermal sclerosis was induced in various mouse strains, although the intensity of dermal sclerosis varied among various strains. Histopathological and biochemical analysis demonstrated that this experimental murine scleroderma reflected a number of aspects of human scleroderma. Further investigation of the cellular and molecular mechanisms of inflammatory reaction, fibroblast activation and extracellular matrix deposition following dermal injury by bleomycin treatment will lead to the better understanding of the pathophysiology and the exploration of effective treatment against scleroderma. This review summarizes recent progress of the cellular and molecular events in the pathogenesis of bleomycin‐induced scleroderma; moreover, further perspective by using this mouse model has been discussed.
Effect of UVB radiation emitted from the narrowband TL‐01 lamp (311 nm) on the calcitriol synthesis in organotypic cultures of keratinocytes
Authors: Lehmann Bodo , Knuschke Peter , Meurer Michael
Published: January 2005

The skin is the only tissue yet known in which the complete UVB‐induced pathway from 7‐dehydrocholesterol (7‐DHC) to hormonally active calcitriol (1α,25‐dihydroxyvitamin D3) occurs under physiological conditions. It is well known that both calcitriol and UVB radiation exert potent antipsoriatic effects. We speculate that the therapeutic effect of UVB radiation can be attributed to UVB‐triggered cutaneous synthesis of calcitriol for which the optimum wavelength was a range of 300 ± 3 nm in vitro and in vivo. On the other hand, the narrowband Philips TL‐01 lamp which is commonly used as UVB source for therapeutical treatment of psoriasis, has a maximum spectral irradiance at around 311 nm. The aim of this study was to investigate the calcitriol‐inducing potential of the TL‐01 lamp in organotypic cultures of keratinocytes supplemented with 25 μM 7‐DHC at different radiant exposures (125–1000 mJ/cm2). We found that the maximum calcitriol‐generating capacity of the TL‐01 lamp at 500 mJ/cm2(corresponding to 2.1 SED [Standard Erythema Dose]) and 16 h after irradiation still amounts to approximately 45 percent of that of monochromatic radiation at 300 nm and 30 mJ/cm2. We conclude from our findings that irradiation with the narrowband TL‐01 lamp in therapeutic dose range can affect calcitriol synthesis in epidermal keratinocytes. Thus, the antipsoriatic effect observed after TL‐01 lamp exposures may be, at least partially, explained by the known action of newly‐synthesized calcitriol on the epidermal cell proliferation and differentiation.
Expression of 25‐hydroxyvitamin D3‐1α‐hydroxylase in malignant melanoma: implications for growth control via local synthesis of 1,25(OH)2D3 and detection of multiple splice variants
Authors: Seifert M. , Diesel B. , Meese E. , Tilgen W. , Reichrath J.
Published: January 2005

1,25‐Dihydroxyvitamin D3, 1,25(OH)2D3) and analogs have been shown to inhibit proliferation and to induce differentiation in various cell types, including human melanocytes. There are two principal enzymes involved in the formation of circulating 1,25(OH)2D3 from vitamin D, the hepatic microsomal or mitochondrial vitamin D 25‐hydroxylase (25‐OHase) and the renal mitochondrial enzyme 25‐hydroxyvitamin D3‐1α‐hydroxylase (1α‐OHase) for vitamin D and 25(OH)D3, respectively. Recently, extra‐renal activity of 1α‐OHase has been reported in various cell types including macrophages, keratinocytes, prostate and colon cancer cells. Increasing evidence indicates that extra‐renal 1α‐OHase may act in many tissues via the local production of 1,25(OH)2D3 as a major regulator of cell growth in an autocrine or paracrine fashion. In human malignant glioma we have demostrated a correlation between amplification of the gene and its overexpression. Using Reverse transcription (RT)‐PCR with primers amplifying a part of the 1α–OHase sequence, we have shown now for the first time several splice variants, including transcripts encoding truncated proteins in melanoma cell lines. To arrive at a more complete description of 1α–OHase expression we developed and employed a highly specific approach that combinded nested and touchdown PCR to clone full length 1α‐OHase. In addition, we identified several new splice variants in human melanoma. The new splice variants that were termed Hyd‐V5, ‐V6, ‐V7 and ‐V8 were cloned and sequenced. All but one of the new variants showed an insertion of intron 1 leading to a premature termination signal and to truncated proteins without ferredoxin and haem‐binding site of the P450 protein. In conclusion our findings indicate that (1) local synthesis of 1,25(OH)2VitD3 mediated via 1α‐OHase may be of high importance for growth characteristics of melanoma cells and (2) 25(OH)VitD3 or other percusors of biologically active vitamin D metabolites may be effective in the palliative treatment of metastasizing melanoma.
Modulation of Vitamin D‐induced growth inhibition in melanoma cell lines: implications for an important function of vitamin D receptor (VDR) and 1,25‐dihydroxyvitamin D3‐24‐hydroxylase (24‐OHase) expression, histonedeacetylation, and calpain activity
Authors: Reichrath Jörg , Rech Martin , Moeini Maryam , Meineke Viktor , Tilgen Wolfgang , Seifert Markus
Published: January 2005

Increasing evidence indicates an important role of the skin vitamin D system for tumorigenesis and progression of malignant melanoma. We have now characterized the vitamin D system in melanoma cell lines, detecting strong RNA expression of vitamin D receptor (VDR), 25‐hydroxyvitamin D‐1α‐hydroxylase (1αOHase), vitamin D‐25‐hydroxylase (25OHase) and 1,25‐dihydroxyvitamin D‐24‐hydroxylase (24OHase) in various melanoma cell lines (MEWO, SKMEL28, BU47HOM) using real time PCR (LightCycler) and specific hybridisation probes. We then have analyzed effects of 1,25‐dihydroxyvitamin D3 and analogs (EB 1089, MC 1288) on proliferation and apoptosis as well as on expression of VDR, 1αOHase), 25OHase, and 24OHase in various melanoma cell lines (BUHOM, MEWO, SKMEL)in vitro. Using a tetrazolium salt (WST‐1) based colorimetric assay, we detected dose‐dependent inhibition of cell growth (up to 40%) induced by calcitriol or its analogs. Treatment of melanoma cells with calcitriol resulted in decreased immunoreactivity of proliferation markers including Ki‐67 and PCNA. Flow cytometry experiments (bcl‐2, bcl‐xl, bcl‐xs, bcl‐x, bax, CD95) and analysis of annexin Pi expression revealed no induction of apoptosis by calcitriol (10−7 M) or its analogs, while increased levels of bcl‐2 protein were detected. Additionally, we show modulation of vitamin D‐induced inhibition of cell proliferation by calpain inhibitors I and II (Calbiochem) as well as by inhibitors of histonedeacetylation (sodium butyrate, trichostatin A). In conclusion our findings indicate that (i) vitamin D analogs suppress proliferation but do not induce apoptosis in melanoma cell lines, (ii) induction of VDR and 24‐OHase expression as well as histonedeacetylation and calpain activity modulate vitamin D‐induced growth inhibition, (iii) new calcitriol analogs exerting less systemic side effects may be interesting candidates for the treatment of metastasizing malignant melanoma.
An evolutionary concept for altered steroid hormone metabolism in patients with rheumatoid arthritis
Authors: Straub Rainer H. , Besedovsky Hugo O.
Published: January 2005

The pathogenesis of chronic disabling inflammatory diseases (CDIDs) is partly understood. The presently used concepts focus mainly on abnormalities of the immune system but this view is incomplete. The presented concept is a new framework for the pathogenesis of CDIDs. It integrates evolutionary theories with the classical immunological standpoint, which is further linked with a neuroendocrine immune view of erroneous homeostatic adaptation of the other supersystems (nervous system, endocrine system, reproductive system): 1. In CDIDs, the loss of tolerance against self and harmless foreign antigens leads to continuous immune aggression which is dependent on a multifactorial genetically polymorph background (the initiation). 2. However, advantageous or disadvantageous adaptation to CDIDs were not evolutionary conserved because CDIDs severely impaired reproduction or appeared after the reproductive phase and, thus, imply a strong negative selection pressure. 3. Reactions of all supersystems are evolutionary conserved for transient inflammatory reactions such as the elimination of infectious agents, wound healing, foreign body reaction and many others. 4. The sum of the false reactions of all supersystems – conserved for transient inflammation – provide the pathogenetic background for the chronification of CDIDs because a continuous aggressive situation is created (the chronification). The human disease of rheumatoid arthritis is used as a prototypic CDID to illustrate the integrated view point. The synovial tissue innervation is in the focus of this concept.
Pro‐differentiating effects of oxysterols in keratinocytes
Authors: Schmuth Matthias , Bikle Dan D. , Willson Tim M. , Mangelsdorf David J. , Elias Peter M. , Feingold Kenneth R.
Published: January 2005

Oxysterols stimulate keratinocyte differentiation, which involves the formation of the cornified envelope on the inner plasma membrane by transglutaminase crosslinking of several constituent proteins. Oxysterols increase the expression of one of these crosslinked proteins, involucrin, which can be abolished by mutations of the distal activator protein (AP)‐1 response element in the involucrin promoter. Here, we show that oxysterols increase AP‐1 binding in electrophoretic gel mobility shift assays and that oxysterols induce the expression of an AP‐1 reporter. We further describe the individual components of the AP‐1 complex, which are involved in the oxysterol‐mediated AP‐1 activation and stimulation of keratinocyte differentiation. We identified Fra‐1 within the AP‐1 DNA binding complex by super shift analysis of nuclear extracts from oxysterol‐treated, cultured keratinocytes. Western blot analysis demonstrated that oxysterol treatment increased the levels of Fra‐1 and Jun‐D, while Northern analysis revealed that oxysterols increased mRNA levels for Fra‐1, c‐Fos and Jun‐D. Together these data indicate that oxysterols stimulate involucrin expression by increasing the levels of specific proteins of the AP‐1 complex, indicating that oxysterols regulate keratinocyte differentiation by inducing the AP‐1 factors, which in turn activate the genes required for epidermal differentiation. The presence of LXREs within the promoter regions of individual AP‐1 proteins suggests that these oxysterol effects may be mediated by LXR.
Sexual hormones utilize complex mechanisms to modulate sebocyte differentiation
Authors: Zouboulis ChC , Chen W. , Alestas Th. , Makrantonaki E , Seltmann H. , Müller‐Decker K
Published: January 2005

Sexual hormones are important in the maintenance of human skin. Being the endocrine “brain” of the skin, the sebaceous gland is a major target of sexual hormones. While androgens stimulate sebocyte proliferation, estrogens do not to affect sebaceous gland growth. Regarding differentiation, androgens are expected to stimulate and estrogens to suppress sebaceous lipid synthesis, while estrogens, in vivo, enhance sebaceous lipogenesis in aged skin. The latter results have been disputed by current in vitro data indicating no direct effect of sexual hormones on sebocyte differentiation. To elucidate these contradictions we have investigated possible pathways which may be used by sexual hormones to modulate sebocyte differentiation in vitro. It has been postulated that androgen induction of lipogenesis requires the concomitant presence of peroxisome proliferator‐activated receptor (PPAR) ligands. We found that arachidonic acid (AA), the direct precursor of leukotriene B4, a natural PPARα ligand, and linoleic acid (LA), a natural PPARδ ligand, induce sebocyte enlargement, accumulation of lipid droplets in the cytoplasm, and nuclear fragmentation. The combined administration of testosterone and AA or LA slightly increased sebaceous lipogenesis. In contrast, synthetic PPAR ligands were unable to enhance sebaceous lipogenesis. Interestingly, AA synthesis in human sebocytes was significantly stimulated by the prostaglandins (PG) E2 and Δ15‐J2. On the other hand, PPARγ expression was downregulated by the phytoestrogen genistein. Interestingly, 17β‐estradiol has previously been shown to induce the metabolism of PGD2 to Δ12‐PGJ2, a natural PPARγ ligand. In addition, we found that 17β‐estradiol increases IGF‐I synthesis (+28%) and down‐regulates IGF‐IR expression (−37 to −48%), whereas IGF‐I significantly induces sebaceous lipogenesis. In conclusion, sexual hormones are not directly active but are likely to utilize complex mechanisms, including modified known pro‐inflammatory pathways, to modulate sebocyte differentiation.