bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variable switching rates of malaria virulence genes are associated with chromosomal position
Authors: Frank Matthias , Dzikowski Ron , Amulic Borko , Deitsch Kirk 
Published: June 2007

SummaryAntigenic variation in Plasmodium falciparum malaria is mediated by transcriptional switches between different members of the multicopy var gene family. Each var gene encodes a member of a group of heterogeneous surface proteins collectively referred to as PfEMP1. Mutually exclusive expression ensures that an individual parasite only transcribes a single var gene at a time. In this work we studied var gene switching to determine if transcriptional switches favour expression of particular subgroups of var genes and if var gene activation within a clonal population of parasites follows a predetermined order. We show that in clonal parasite populations, expression of var genes located in the central regions of chromosomes is remarkably stable and that they rarely undergo transcriptional switches in the absence of selection. In contrast, parasites expressing subtelomerically located var genes readily switched to alternative var loci. We confirmed these observations by generating transgenic parasites carrying drug selectable markers in subtelomeric and central var loci and monitoring switching after release from selection. Our data show that different var genes have different intrinsic switching rates that correlate with chromosomal location, and that there is no predetermined order of expression.
Acquisition of a natural resistance gene renders a clinical strain of methicillin‐resistantStaphylococcus aureusresistant to the synthetic antibiotic linezolid
Authors: Toh Seok‐Ming , Xiong Liqun , Arias Cesar A. , Villegas Maria V. , Lolans Karen , Quinn John , Mankin Alexander S. 
Published: June 2007

SummaryLinezolid, which targets the ribosome, is a new synthetic antibiotic that is used for treatment of infections caused by Gram‐positive pathogens. Clinical resistance to linezolid, so far, has been developing only slowly and has involved exclusively target site mutations. We have discovered that linezolid resistance in a methicillin‐resistantStaphylococcus aureushospital strain from Colombia is determined by the presence of thecfrgene whose product, Cfr methyltransferase, modifies adenosine at position 2503 in 23S rRNA in the large ribosomal subunit. The molecular model of the linezolid–ribosome complex reveals localization of A2503 within the drug binding site. The natural function ofcfrlikely involves protection against natural antibiotics whose site of action overlaps that of linezolid. In the chromosome of the clinical strain,cfris linked toermB, a gene responsible for dimethylation of A2058 in 23S rRNA. Coexpression of these two genes confers resistance to all the clinically relevant antibiotics that target the large ribosomal subunit. The association of theermB/cfroperon with transposon and plasmid genetic elements indicates its possible mobile nature. This is the first example of clinical resistance to the synthetic drug linezolid which involves a natural resistance gene with the capability of disseminating among Gram‐positive pathogenic strains.
The Mycobacterium tuberculosis FAS‐II condensing enzymes: their role in mycolic acid biosynthesis, acid‐fastness, pathogenesis and in future drug development
Authors: Bhatt Apoorva , Molle Virginie , Besra Gurdyal S. , Jacobs William R. , Kremer Laurent 
Published: June 2007

SummaryMycolic acids are very long‐chain fatty acids representing essential components of the mycobacterial cell wall. Considering their importance, characterization of key enzymes participating in mycolic acid biosynthesis not only allows an understanding of their role in the physiology of mycobacteria, but also might lead to the identification of new drug targets. Mycolates are synthesized by at least two discrete elongation systems, the type I and type II fatty acid synthases (FAS‐I and FAS‐II respectively). Among the FAS‐II components, the condensing enzymes that catalyse the formation of carbon‐carbon bonds have received considerable interest. Four condensases participate in initiation (mtFabH), elongation (KasA and KasB) and termination (Pks13) steps, leading to full‐length mycolates. We present the recent biochemical and structural data for these important enzymes. Special emphasis is given to their role in growth, intracellular survival, biofilm formation, as well as in the physiopathology of tuberculosis. Recent studies demonstrated that phosphorylation of these enzymes by mycobacterial kinases affects their activities. We propose here a model in which kinases that sense environmental changes can phosphorylate the condensing enzymes, thus representing a novel mechanism of regulating mycolic acid biosynthesis. Finally, we discuss the attractiveness of these enzymes as valid targets for future antituberculosis drug development.
Subcellular localization of Escherichia coli osmosensory transporter ProP: focus on cardiolipin membrane domains
Authors: Mileykovskaya Eugenia 
Published: June 2007

SummaryThe role for specific lipids in the spatial distribution of the membrane proteins and formation of the lipid‐protein membrane domains is an emerging theme in the studies of the supramolecular organization of the bacterial cell. A combination of the lipid and protein visualization techniques with manipulation of the cell lipid composition provides a useful tool for these studies. This MicroCommentary reviews the first experimental example demonstrating an involvement of the phospholipid cardiolipin in recruitment of a membrane protein (specifically H+‐osmoprotectant symporter ProP) to the Escherichia coli cell poles. The properties of cardiolipin domains employed in creating a specific environment for structural organization and function of membrane protein complexes are also discussed.
A novel lysis system in PM2, a lipid‐containing marine double‐stranded DNA bacteriophage
Authors: Krupovič Mart , Daugelavičius Rimantas , Bamford Dennis H. 
Published: June 2007

SummaryIn this study we investigated the lysis system of the lipid‐containing double‐stranded DNA bacteriophage PM2 infecting Gram‐negative marine Pseudoalteromonas species. We analysed wt and lysis‐deficient phage‐induced changes in the host physiology and ascribed functions to two PM2 gene products (gp) involved in lysis. We show that bacteriophage PM2 uses a novel system to disrupt the infected cell. The novelty is based on the following findings: (i) gp k is needed for the permeabilization of the cytoplasmic membrane and appears to play the role of a typical holin. However, its unique primary structure [53 aa, 1 transmembrane domain (TMD)] places it into a new class of holins. (ii) We have proposed that, unlike other bacteriophages studied, PM2 relies on lytic factors of the cellular origin for digestion of the peptidoglycan. (iii) gp l (51 aa, no TMDs) is needed for disruption of the outer membrane, which is highly rigidified by the divalent cations abundant in the marine environment. The gp l has no precedent in other phage lytic systems studied so far. However, the presence of open reading frame l‐like genes in genomes of other bacterial viruses suggests that the same system might be used by other phages and is not unique to PM2.
Brooke–Spiegler syndrome – report of four families: treatment with CO2 laser
Authors: Retamar Roberto Adrián , Stengel F. , Saadi M. E. , Kien M. C. , Della Giovana P. , Cabrera H. , Chouela E. N. 
Published: June 2007

AbstractBackground  Brooke–Spiegler syndrome is a well known but rare cutaneous disorder characterized by the presence of multiple trichoepitheliomas and cylindromas.Methods  Four families with Brooke–Spiegler syndrome are described.Results  Spiradenomas developed on the back in two patients. A CO2 laser was used to treat facial trichoepitheliomas in two patients with good results.Conclusions  The large number of facial lesions in this syndrome often produce a significant emotional impact. We believe that it is important to provide patients with a good therapeutic option. CO2 laser therapy may fill this role.
Patient education and regular surveillance results in earlier diagnosis of second primary melanoma
Authors: Uliasz Annemarie , Lebwohl Mark 
Published: June 2007

AbstractBackground  As the incidence of cutaneous melanoma continues to rise, more individuals will be at risk for developing second primary melanomas. We hypothesize that patient education and follow‐up surveillance will lead to the early detection of subsequent primary melanomas as demonstrated by a decrease in Breslow thickness at diagnosis.Methods  A computer‐based investigation was performed to identify patients who had developed a second primary melanoma following treatment of in situ and American Joint Commission on Cancer (AJCC) Stage I or II melanoma. Patients are routinely educated on the increased risk of developing a second primary lesion and characteristic clinical features of melanoma. Patient surveillance was performed on a regular basis. Differences in Breslow thickness between the initial and subsequent primary melanomas were analyzed by a paired t‐test.Results  Among 877 individuals identified in the Mount Sinai School of Medicine Department of Dermatopathology database with in situ or AJCC Stage I or II melanoma, 111 developed a second primary melanoma. The mean thickness was 0.239 ± 0.661 mm for the initial melanoma and 0.1135 ± 0.319 mm for the subsequent melanoma. By paired t‐test, the difference in tumor thickness was statistically significant (P = 0.019).Conclusions  Upon analysis of our data, subsequent primary cutaneous melanomas were found to be significantly thinner than initial primary melanomas at the time of diagnosis. This suggests that earlier diagnosis may be the result of patient education and careful follow up. Counselling on the risk of developing a second primary melanoma, education regarding clinical characteristics of melanoma, and routine lifelong follow up should be provided to all patients diagnosed with a cutaneous melanoma.
Cutaneous phaeohyphomycosis caused by Veronaea botryosa observed as sclerotic cells in tissue
Authors: Kondo Yukiko , Hiruma Masataro , Matsushita Akiko , Matsuba Shoichi , Nishimura Kazuko , Takamori Kenji 
Published: June 2007

A 65‐year‐old Japanese female farmer had an erythematous, slightly scaly, indurated plaque on the dorsum of the left wrist of more than 3 years’ duration. She had a history of hepatitis C. Her medical history and family history were otherwise unremarkable. The lesion had begun as a small region of erythema on the dorsum of the left wrist 3 years previously and had gradually enlarged. The patient had seen a local physician and had been treated with topical steroids, topical antifungals, and topical vitamin D3 agents without improvement.Initial laboratory studies revealed slightly decreased numbers of white blood cells and thrombocytes, decreased albumin levels, and elevated liver enzymes, reflecting chronic hepatitis C. Clinical examination of the lesion revealed a well‐demarcated, erythematous, slightly scaly, indurated plaque of 22 mm × 28 mm in size on the dorsum of the left wrist (Fig. 1). Superficial lymph nodes were nonpalpable. Direct microscopy revealed aggregates of thick‐walled spores, considered to be sclerotic cells, from which budding brown hyphae emanated (Fig. 2a).A well‐demarcated, erythematous, slightly scaly, indurated plaque of 22 mm × 28 mm in size on the dorsum of the left wristimage(a) Microphotograph of scales in KOH reveals aggregates of thick‐walled, brown sclerotic cells and budding brown hyphae (×400). (b) Conidia are bicellular, gourd‐shaped at maturity and pale brown. They are sympodially produced by darker conidiogenous cells (slide culture, ×400)imageCutaneous biopsy specimens revealed a chronic granulomatous inflammation infiltrated with lymphocytes, histiocytes, neutrophils, and multinucleated giant cells. Within the microabscess and within one of the giant cells were large, brown, thick‐walled cells, which were identified as sclerotic cells, and brown septate hyphae.Culture on a Sabouraud dextrose agar slant at 26 °C yielded villous, green‐tinged, black–gray colonies, with a central button‐like protuberance. By 28 days, these colonies had reached 4.8 cm in diameter. A slide culture showed pale brown septate hyphae bearing lateral and terminal conidiophores. Conidiophores were erect, straight, or flexuous, unbranched or occasionally loosely branched, smooth‐walled, septate, and brown. Conidiogenous cells were terminal or lateral and cylindrical in the apical part with numerous dark brown scars fading away to the apex. Conidia were sympodial and bicellular, with rounded apices and truncated bases (Fig. 2b). On the basis of these morphologic features, we identified the mold as Veronaea botryosa. Surgical excision of the lesion was performed, resulting in complete healing.
Urachal duct remnant‐like umbilical clear cell acanthoma in an infant: An unusual presentation and pitfall in clinical practice
Authors: Hsu Hsiu‐cheng , Yang Chih‐Hsun , Kuo Tseng‐tong , Shih I‐Hsin , Hong Hong‐Shang 
Published: June 2007

AbstractBackground  Although an umbilical nodule is common in neonates and young infants, an umbilical nodule of poor therapeutic response will increase the likelihood of other uncommon etiology. Clear cell acanthoma (CCA) has never been described as an oozing umbilical nodule on infants.Methods  To present a case of CCA which occurred on an 8‐month‐old female infant presenting with one weeping nodule on the umbilicus since early neonate. The lesion underwent skin biopsy and subsequent hematoxylin‐eosin and periodic acid‐Schiff staining.Result  Three courses of liquid nitrogen cryosurgery were performed after the diagnosis of CCA was confirmed. The lesion resolved rapidly.Conclusion  This report presents the first and youngest case of umbilical CCA in the English literature. This case supports the inflammatory dermatosic nature of CCA.
Thiazolidinediones in dermatology
Authors: Boyd Alan S. 
Published: June 2007

AbstractThiazolidinediones, also known as glitazones, represent a relatively new class of medication used for glycemic control in patients with type II diabetes mellitus. These drugs interact with the peroxisome proliferator‐activated receptor γ, a member of the nuclear receptor superfamily, which in turn heterodimerizes with retinoid X receptors to stimulate gene transcription. At a physiologic level, glitazones stimulate adipocyte differentiation, enhance insulin‐sensitive glucose uptake by muscle and fat cells, suppress angiogenesis, inhibit tumor cell growth, and normalize keratinocyte differentiation. They have also demonstrated the capacity to diminish inflammatory cytokine production, most notably, that of tumor necrosis factor α. Patients with such disparate conditions as psoriasis, hirsutism, melanoma, angiosarcoma, lipodystrophy, and necrobiosis lipoidica have benefited from the administration of thiazolidinediones. Clinicians should become familiar with glitazones as they are experiencing a burgeoning use among patients with non‐insulin‐dependent diabetes mellitus and have demonstrated clinical efficacy in treating certain skin conditions.
Adaptation in a spider mite population after long‐term evolution on a single host plant
Authors: MAGALHÃES S. , FAYARD J. , JANSSEN A. , CARBONELL D. , OLIVIERI I. 
Published: June 2007

AbstractEvolution in a single environment is expected to erode genetic variability, thereby precluding adaptation to novel environments. To test this, a large population of spider mites kept on cucumber for approximately 300 generations was used to establish populations on novel host plants (tomato or pepper), and changes in traits associated to adaptation were measured after 15 generations. Using a half‐sib design, we investigated whether trait changes were related to genetic variation in the base population. Juvenile survival and fecundity exhibited genetic variation and increased in experimental populations on novel hosts. Conversely, no variation was detected for host choice and developmental time and these traits did not evolve. Longevity remained unchanged on novel hosts despite the presence of genetic variation, suggesting weak selection for this trait. Hence, patterns of evolutionary changes generally matched those of genetic variation, and changes in some traits were not hindered by long‐term evolution in a constant environment.
Ability of chromosome 4H to compensate for 4D in response to drought stress in a newly developed and identified wheat–barley 4H(4D) disomic substitution line
Authors: Molnár I. , Linc G. , Dulai S. , Nagy E. D. , Molnár‐Láng M. 
Published: June 2007

AbstractA spontaneously developed wheat–barley 4H(4D) disomic substitution line was identified cytogenetically using genomic in situ hybridization (GISH), multicolour fluorescent in situ hybridization (FISH) and microsatellite markers. The ability of the barley 4H chromosome to compensate for wheat 4D in response to mild drought stress was also investigated. In the barley cv. ‘Betzes’ and the 4H(4D) substitution line, mild osmotic stress induced intensive stomatal closure, resulting in reduced water loss through transpiration and unchanged relative water content in the leaves. As the CO2 assimilation rate remained relatively high, the water use efficiency, which is an important factor associated with drought tolerance, increased extensively under mild osmotic stress in these lines. In the case of the parental wheat genotypes, however, mild drought stress induced less intense stomatal closure and a greater decrease in the CO2 assimilation rate than in barley or in the substitution line, resulting in unaugmented or reduced water use efficiency. The results demonstrate that genes localised on the 4H chromosome of barley were able to increase the water use efficiency of the wheat substitution line, which is suitable for improving wheat drought tolerance through intergeneric crossing.
Discovery and genotyping of high‐throughput SNP markers for crown rust resistance gene Pc94 in cultivated oat
Authors: Chen G. , Chong J. , Prashar S. , Procunier J. D. 
Published: June 2007

AbstractCrown rust caused by Puccinia coronata f. sp. avenae Eriks is a serious problem for oat production worldwide and pyramiding multiple resistance genes into new cultivars is a key objective of breeders. Many race specific resistance genes have been mapped and markers that are closely linked to them have been identified. However, the use of these markers in oat breeding practice has been limited due to the economics of marker assisted selection (MAS) deployment. Single nucleotide polymorphism (SNP) markers have been demonstrated to have a high‐throughput capability with relatively low cost and numerous semi‐automated SNP scoring platforms exist. Gene Pc94 has remained highly effective since it was first tested on the Canadian crown rust populations in 1993 and is one of the few effective genes available in Western Canada. In the present study, PCR products were amplified using primers derived from sequences of amplified fragment length polymorphism bands which have been shown to be linked to Pc94. Genomic DNA from genotypes, with and without the Pc94 gene, were used as the PCR templates. By comparative sequence alignment amongst the PCR fragments, many putative SNP sites were identified. From these sites, four SNP sites were selected and validated by the single base extension method. One SNP site, Pc94‐SNP1a, was tested on two F2:3 populations segregating for the resistance gene. The map distances between the SNP marker and Pc94 were 2.1 and 5.4 cM in the two different populations. Various oat cultivars and germplasm lines were also tested for a wider application of the SNP marker. Fluorescent technology and capillary electrophoresis allowed for the semi‐automated, fairly high‐throughput scoring of the SNP markers.
Development of the male gametophyte of an infertile plant Armoracia rusticana Gaertn.
Authors: Winiarczyk K. , Tchórzewska D. , Bednara J. 
Published: June 2007

AbstractHorseradish, Armoracia rusticana, is propagated vegetatively through root cuttings. It is described as a male‐sterile plant as it does not form seeds or only develops them in small quantities. This study discusses the anatomical structure of anthers and the events throughout meiosis up to the formation of a male gametophyte. Microscopic observations have shown that the anatomical structure of the anther wall of A. rusticana is typical of the whole family of Brassicaceae, and all its layers are properly developed and fully functional. Meiosis in the sporogenous tissue proceeds correctly and leads to the formation of microspores. Also the configurations of the cytoplasmic skeleton are typical of plants with simultaneous cytokinesis. Further development, however, exhibits many abnormalities. A majority of the cells formed in the sample studied were dysfunctional uninucleate microspores with apparent symptoms of degeneration of the cytoplasm and organelles. Binucleate pollen grains, in which mitosis did occur, constituted only 10% of the cells analysed. Anatomical and cytological observations of male sterility in A. rusticana indicated inhibition of development at the microspore, stage which was manifested by cytoplasm degeneration with a low number of membranes and a scarce amount of starch in proplastids. Usually, in the prolonged microspore stage and in the young pollen no mitosis occurs at the time of anthesis. Cytological disorders may, to a great extent, limit the number of functional bicellular male gametophytes. Both in microspores and in pollen grains, there is exceptionally little starch in plastids.
Relationship between molecular marker heterozygosity and hybrid performance in intra‐ and interspecific hybrids of cotton
Authors: Zhang X. Q. , Wang X. D. , Jiang P. D. , Hua S. J. , Zhang H. P. , Dutt Y. 
Published: June 2007

AbstractThe present study was conducted to investigate the relationship between parental molecular marker diversity and hybrid performance in both intra‐ and interspecific hybrids of cotton to evaluate the feasibility of predicting hybrid performance using molecular markers. Three cytoplasmic male sterile (CMS) lines were crossed with 10 restorer lines to produce 22 F1 hybrids during 2003. Of 22 F1s, 14 hybrids were intraspecific (Gossypium hirsutum × G. hirsutum) and eight interspecific (G. hirsutum × G. barbadense). These 22 F1 hybrids and their parents were evaluated for yield and fibre quality traits at Zhejiang University, Hangzhou, China during 2004 and 2005. Genetic distances (GD) among the parents were calculated from 56 random‐amplified polymorphic DNAs (RAPD) and 66 simple sequence repeat (SSR) marker data, and their correlation with hybrid performance and heterosis were analysed. The parents could be discriminated into G. hirsutum and G. barbadense clusters by cluster analysis based on both RAPD and SSR markers data. The correlation (r = 0.503, P ≤ 0.05) was calculated between GDrapd (GD based on RAPD markers) and GDssr (GD based on SSR markers). Correlation of GD with hybrid performance and heterosis differed considerably between intra‐ and interspecific hybrids. The correlation between GD and hybrid performance was non‐significant for most of traits within the hybrids of G. hirsutum species. However, it was significantly and positively correlated for fibre length, fibre strength and elongation in interspecific hybrids. The relationship between GD and heterosis was observed to be positively significant for boll weight within hybrids of G. hirsutum with significant and negative correlations for fibre length and elongation. In conclusion, the power of predicting hybrid performance using molecular markers in cotton is low. But, the relationship between SSR marker heterozygosity and hybrid performance can be used to predict fibre length during interspecific hybrid cotton breeding.