bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic Dissection of Parallel Sister-Chromatid Cohesion Pathways
Authors: Xu Hong , Boone Charles , Brown Grant W 
Published: May 2007

Abstract
Sister-chromatid cohesion, the process of pairing replicated chromosomes during mitosis and meiosis, is mediated through the essential cohesin complex and a number of nonessential cohesion genes, but the specific roles of these nonessential genes in sister-chromatid cohesion remain to be clarified. We analyzed sister-chromatid cohesion in double mutants of mrc1Δ, tof1Δ, and csm3Δ and identified additive cohesion defects that indicated the existence of at least two pathways that contribute to sister-chromatid cohesion. To understand the relationship of other nonessential cohesion genes with respect to these two pathways, pairwise combinations of deletion and temperature-sensitive alleles were tested for cohesion defects. These data defined two cohesion pathways, one containing CSM3, TOF1, CTF4, and CHL1, and the second containing MRC1, CTF18, CTF8, and DCC1. Furthermore, we found that the nonessential genes are not important for the maintenance of cohesion at G2/M. Thus, our data suggest that nonessential cohesion genes make critical redundant contributions to the establishment of sister-chromatid cohesion and define two cohesion pathways, thereby establishing a framework for understanding the role of nonessential genes in sister-chromatid cohesion.
Manipulating Mitotic Recombination in the Zebrafish Embryo Through RecQ Helicases
Authors: Xie Jing , Bessling Seneca L , Cooper Timothy K , Dietz Harry C , McCallion Andrew S , Fisher Shannon 
Published: May 2007

Abstract
RecQ DNA helicases resolve Rad-51-mediated recombination and suppress aberrant homologous recombination. RecQ gene loss is associated with cancer susceptibility and increased mitotic recombination. We have developed an in vivo assay based on a zebrafish pigment mutant for suppression of RecQ activity, and demonstrate that zebrafish RecQ genes have conserved function in suppressing mitotic recombination.
A Mutant Allele of the Transcription Factor IIH Helicase Gene, RAD3, Promotes Loss of Heterozygosity in Response to a DNA Replication Defect in Saccharomyces cerevisiae
Authors: Navarro Michelle S , Bi Liu , Bailis Adam M 
Published: May 2007

Abstract
Increased mitotic recombination enhances the risk for loss of heterozygosity, which contributes to the generation of cancer in humans. Defective DNA replication can result in elevated levels of recombination as well as mutagenesis and chromosome loss. In the yeast Saccharomyces cerevisiae, a null allele of the RAD27 gene, which encodes a structure-specific nuclease involved in Okazaki fragment processing, stimulates mutation and homologous recombination. Similarly, rad3-102, an allele of the gene RAD3, which encodes an essential helicase subunit of the core TFIIH transcription initiation and DNA repairosome complexes confers a hyper-recombinagenic and hypermutagenic phenotype. Combining the rad27 null allele with rad3-102 dramatically stimulated interhomolog recombination and chromosome loss but did not affect unequal sister-chromatid recombination, direct-repeat recombination, or mutation. Interestingly, the percentage of cells with Rad52-YFP foci also increased in the double-mutant haploids, suggesting that rad3-102 may increase lesions that elicit a response by the recombination machinery or, alternatively, stabilize recombinagenic lesions generated by DNA replication failure. This net increase in lesions led to a synthetic growth defect in haploids that is relieved in diploids, consistent with rad3-102 stimulating the generation and rescue of collapsed replication forks by recombination between homologs.
Frequency-Dependent Selection and the Maintenance of Genetic Variation: Exploring the Parameter Space of the Multiallelic Pairwise Interaction Model
Authors: Trotter Meredith V , Spencer Hamish G 
Published: May 2007

Abstract
When individuals' fitnesses depend on the genetic composition of the population in which they are found, selection is then frequency dependent. Frequency-dependent selection (FDS) is often invoked as a heuristic explanation for the maintenance of large numbers of alleles at a locus. The pairwise interaction model is a general model of FDS via intraspecific competition at the genotypic level. Here we use a parameter-space approach to investigate the full potential for the maintenance of multiallelic equilibria under the pairwise interaction model. We find that FDS maintains full polymorphism more often than classic constant-selection models and produces more skewed equilibrium allele frequencies. Fitness sets with some degree of rare advantage maintained full polymorphism most often, but a wide variety of nonobvious fitness patterns were also found to have positive potential for polymorphism. An example is put forth suggesting possible explanations for multiallelic polymorphisms maintained despite positive FDS on individual alleles.
Genetic Load in Sexual and Asexual Diploids: Segregation, Dominance and Genetic Drift
Authors: Haag Christoph R , Roze Denis 
Published: May 2007

Abstract
In diploid organisms, sexual reproduction rearranges allelic combinations between loci (recombination) as well as within loci (segregation). Several studies have analyzed the effect of segregation on the genetic load due to recurrent deleterious mutations, but considered infinite populations, thus neglecting the effects of genetic drift. Here, we use single-locus models to explore the combined effects of segregation, selection, and drift. We find that, for partly recessive deleterious alleles, segregation affects both the deterministic component of the change in allele frequencies and the stochastic component due to drift. As a result, we find that the mutation load may be far greater in asexuals than in sexuals in finite and/or subdivided populations. In finite populations, this effect arises primarily because, in the absence of segregation, heterozygotes may reach high frequencies due to drift, while homozygotes are still efficiently selected against; this is not possible with segregation, as matings between heterozygotes constantly produce new homozygotes. If deleterious alleles are partly, but not fully recessive, this causes an excess load in asexuals at intermediate population sizes. In subdivided populations without extinction, drift mostly occurs locally, which reduces the efficiency of selection in both sexuals and asexuals, but does not lead to global fixation. Yet, local drift is stronger in asexuals than in sexuals, leading to a higher mutation load in asexuals. In metapopulations with turnover, global drift becomes again important, leading to similar results as in finite, unstructured populations. Overall, the mutation load that arises through the absence of segregation in asexuals may greatly exceed previous predictions that ignored genetic drift.
Phosphorylation of the Sic1 Inhibitor of B-Type Cyclins in Saccharomyces cerevisiae Is Not Essential but Contributes to Cell Cycle Robustness
Authors: Cross Frederick R , Schroeder Lea , Bean James M 
Published: May 2007

Abstract
In budding yeast, B-type cyclin (Clb)-dependent kinase activity is essential for S phase and mitosis. In newborn G1 cells, Clb kinase accumulation is blocked, in part because of the Sic1 stoichiometric inhibitor. Previous results strongly suggested that G1 cyclin-dependent Sic1 phosphorylation, and its consequent degradation, is essential for S phase. However, cells containing a precise endogenous gene replacement of SIC1 with SIC1-0P (all nine phosphorylation sites mutated) were fully viable. Unphosphorylatable Sic1 was abundant and nuclear throughout the cell cycle and effectively inhibited Clb kinase in vitro. SIC1-0P cells had a lengthened G1 and increased G1 cyclin transcriptional activation and variable delays in the budded part of the cell cycle. SIC1-0P was lethal when combined with deletion of CLB2, CLB3, or CLB5, the major B-type cyclins. Sic1 phosphorylation provides a sharp link between G1 cyclin activation and Clb kinase activation, but failure of Sic1 phosphorylation and proteolysis imposes a variable cell cycle delay and extreme sensitivity to B-type cyclin dosage, rather than a lethal cell cycle block.
Interleukin 22 Is a Candidate Gene forTmevp3, a Locus Controlling Theiler's Virus-Induced Neurological Diseases
Authors: Levillayer F , Mas M , Levi-Acobas F , Brahic M , Bureau J F 
Published: May 2007

AbstractAfter intracerebral inoculation, Theiler's virus induces in its natural host, the mouse, an acute encephalomyelitis followed, in susceptible animals, by chronic inflammation and primary demyelination. Susceptibility to demyelination among strains of laboratory mice is explained by the capacity of the immune system to control viral load during persistence. Also, differences of susceptibility to viral load between the susceptible SJL strain and the resistant B10.S strain are mainly due to two loci, Tmevp2 and Tmevp3, located close to the Ifng locus on chromosome 10. In this article, we show that the Tmevp3 locus controls both mortality during the acute encephalomyelitis and viral load during persistence. Most probably, two genes located in the Tmevp3 interval control these two different phenotypes with efficiencies that depend on the age of the mouse at inoculation. Il22, a member of the IL-10 cytokine family, is a candidate gene for the control of mortality during the acute encephalomyelitis.
Reducing DNA Polymerase α in the Absence of Drosophila ATR Leads to P53-Dependent Apoptosis and Developmental Defects
Authors: LaRocque Jeannine R , Dougherty Diana L , Hussain Sumreen K , Sekelsky Jeff 
Published: May 2007

Abstract
The ability to respond to DNA damage and incomplete replication ensures proper duplication and stability of the genome. Two checkpoint kinases, ATM and ATR, are required for DNA damage and replication checkpoint responses. In Drosophila, the ATR ortholog (MEI-41) is essential for preventing entry into mitosis in the presence of DNA damage. In the absence of MEI-41, heterozygosity for the E(mus304) mutation causes rough eyes. We found that E(mus304) is a mutation in DNApol-α180, which encodes the catalytic subunit of DNA polymerase α. We did not find any defects resulting from reducing Polα by itself. However, reducing Polα in the absence of MEI-41 resulted in elevated P53-dependent apoptosis, rough eyes, and increased genomic instability. Reducing Polα in mutants that lack downstream components of the DNA damage checkpoint (DmChk1 and DmChk2) results in the same defects. Furthermore, reducing levels of mitotic cyclins rescues both phenotypes. We suggest that reducing Polα slows replication, imposing an essential requirement for the MEI-41-dependent checkpoint for maintenance of genome stability, cell survival, and proper development. This work demonstrates a critical contribution of the checkpoint function of MEI-41 in responding to endogenous damage.
The Evolution of Condition-Dependent Sex in the Face of High Costs
Authors: Hadany Lilach , Otto Sarah P 
Published: May 2007

AbstractFacultatively sexual organisms often engage in sex more often when in poor condition. We show that such condition-dependent sex carries evolutionary advantages and can explain the evolution of sexual reproduction even when sex entails high costs. Specifically, we show that alleles promoting individuals of low fitness to have sex more often than individuals of high fitness spread through a population. Such alleles are more likely to segregate out of bad genetic backgrounds and onto good genetic backgrounds, where they tend to remain. This “abandon-ship” mechanism provides a plausible model for the evolution and maintenance of facultative sex.
Mutational Bias for Body Size in Rhabditid Nematodes
Authors: Ostrow Dejerianne , Phillips Naomi , Avalos Arián , Blanton Dustin , Boggs Ashley , Keller Thomas , Levy Laura , Rosenbloom Jeffrey , Baer Charles F 
Published: May 2007

Abstract
Mutational bias is a potentially important agent of evolution, but it is difficult to disentangle the effects of mutation from those of natural selection. Mutation-accumulation experiments, in which mutations are allowed to accumulate at very small population size, thus minimizing the efficiency of natural selection, are the best way to separate the effects of mutation from those of selection. Body size varies greatly among species of nematode in the family rhabditidae; mutational biases are both a potential cause and a consequence of that variation. We report data on the cumulative effects of mutations that affect body size in three species of rhabditid nematode that vary fivefold in adult size. Results are very consistent with previous studies of mutations underlying fitness in the same strains: two strains of Caenorhabditis briggsae decline in body size about twice as fast as two strains of C. elegans, with a concomitant higher point estimate of the genomic mutation rate; the confamilial Oscheius myriophila is intermediate. There is an overall mutational bias, such that mutations reduce size on average, but the bias appears consistent between species. The genetic correlation between mutations that affect size and those underlying fitness is large and positive, on average.
Knowledge-Dependent Pattern Classification of Human Nasal Profiles
Authors: Tanikawa Chihiro , Kakiuchi Yasuhiro , Yagi Masakazu , Miyata Kayoko , Takada Kenji 
Published: May 2007

Abstract
Objective: (1) To determine feature vector representations (geometric pattern parameters) that are effective in describing human nasal profiles, (2) to determine the number of code vectors (typical nasal patterns) that are mathematically optimized by applying the vector quantization method to each feature vector extracted for each subject, and (3) to determine the morphological traits of each code.
Materials and Methods: Lateral facial photographs of 200 Japanese women recorded for orthodontic diagnosis were selected. Five anatomic landmarks were identified on each image together with a set of data points that constituted the contour of the facial profile. An eight-dimensional feature vector effective in distinguishing differences in nasal profile patterns was extracted from the data set using experts' knowledge of the anatomic traits of the nose. The vector quantization technique was applied to the feature vectors to provide the optimum number of nasal profile patterns.
Results: The number of code vectors mathematically optimized was six, and the differences between vectors were maximized by morphological traits of the root, dorsum, tip, and base of the nose. Proportions of the number of image records classified into each code were 25.5%, 24.5%, 21.5%, 15.0%, 10.0%, and 3.5% from code 1 to code 6, respectively.
Conclusions: Classifying nasal profile patterns based on knowledge from a linguistic description was found to be more effective than a method based on uniform sectioning. The differences between vectors were maximized by morphological traits of the root, the dorsum, the tip, and the base of the nose.
Mandibular Symphyseal Distraction Osteogenesis Using a Bone-Supported Distractor
Authors: Bayram Mehmet , Özer Mete , Alkan Alper 
Published: May 2007

Abstract
Increases in mandibular width by symphyseal distraction osteogenesis have recently been shown to be an acceptable and stable treatment option for transverse deficiencies. This case report presents the application of symphyseal distraction osteogenesis for increasing mandibular width using a bone-supported distractor as part of the orthodontic treatment of a 14-year-old male with a tapered shaped mandible and severe mandibular anterior crowding.
Thin-plate Spline Analysis of Craniofacial Growth in Class I and Class II Subjects
Authors: Franchi Lorenzo , Baccetti Tiziano , Stahl Franka , McNamara James A. 
Published: May 2007

Abstract
Objective: To compare the craniofacial growth characteristics of untreated subjects with Class II division 1 malocclusion with those of subjects with normal (Class I) occlusion from the prepubertal through the postpubertal stages of development.
Materials and Methods: The Class II division 1 sample consisted of 17 subjects (11 boys and six girls). The Class I sample also consisted of 17 subjects (13 boys and four girls). Three craniofacial regions (cranial base, maxilla, and mandible) were analyzed on the lateral cephalograms of the subjects in both groups by means of thin-plate spline analysis at T1 (prepubertal) and T2 (postpubertal). Both cross-sectional and longitudinal comparisons were performed on both size and shape differences between the two groups.
Results: The results showed an increased cranial base angulation as a morphological feature of Class II malocclusion at the prepubertal developmental phase. Maxillary changes in either shape or size were not significant. Subjects with Class II malocclusion exhibited a significant deficiency in the size of the mandible at the completion of active craniofacial growth as compared with Class I subjects.
Conclusion: A significant deficiency in the size of the mandible became apparent in Class II subjects during the circumpubertal period and it was still present at the completion of active craniofacial growth.
Root Resorption on Torqued Human Premolars Shown by Tartrate-Resistant Acid Phosphatase Histochemistry and Transmission Electron Microscopy
Authors: Casa Mauricio A. , Faltin Rolf M. , Faltin Kurt , Arana-Chavez Victor E. 
Published: May 2007

Abstract
Objective: To identify clastic cells on the root surfaces of torqued human premolars.
Materials and Methods: A continuous force of 600 cNmm was applied to upper first premolars in patients 13–16 years of age by using a precise biomechanical model with superelastic wires (NiTi-SE). The 28 teeth in 14 patients were divided into five groups (control [nonmoved], and moved for either 1, 2, 3, or 4 weeks) and processed for tartrate-resistant acid phosphatase (TRAP) histochemistry and transmission electron microscopy.
Results: Mononuclear TRAP-positive cells appeared at 2 weeks, wheras large multinucleated TRAP-positive cells were numerous at 3 and 4 weeks. Ultrastructural examination revealed many clastic cells in contact with resorption lacunae. In addition, some cementoblast-like cells appeared secreting new cementum over previously resorbed lacunae.
Conclusions: In general, resorption lacunae and the number of clastic cells, which increased with the duration of the applied force, were found on the cementum surface at the pressure areas. Some signs of cementum repair were also noticed, even with the maintenance of the level of the force.
Orthodontic and Periodontal Outcomes of Treated Impacted Maxillary Canines
Authors: Crescini Aldo , Nieri Michele , Buti Jacopo , Baccetti Tiziano , Pini Prato Giovan Paolo 
Published: May 2007

Abstract
Objective: To evaluate the influence of pretreatment radiographic features (α-angle, d-distance, and s-sector) on (1) the duration of active orthodontic traction and (2) the posttreatment periodontal status (pocket depth [PD] and keratinized tissue width [KT]) of impacted maxillary canines treated by a combined surgical (flap approach) and orthodontic (direct traction to the center of the ridge) treatment.
Material and Methods: A study population of 168 patients (168 canines) was evaluated. Multiple regression analysis was used.
Results: Pretreatment radiographic variables were associated significantly with the duration of orthodontic traction. Age, sex, and site of impaction did not significantly affect the duration of traction. No significant differences in PD and KT were present at the end of surgical-orthodontic treatment with respect to any of the variables considered. The analysis of PD and KT variables after orthodontic treatment revealed a healthy periodontium.
Conclusions: α-angle, d-distance, and s-sector are valid indicators for the duration of orthodontic traction. They are not prognostic indicators of final periodontal status of orthodontically-repositioned canines.
Treatment of a Patient with Multiple Impacted Teeth
Authors: Conley Richard Scott , Boyd Scott B. , Legan Harry L. , Jernigan Christopher C. , Starling Craig , Potts Christopher 
Published: May 2007

Abstract
An impacted or missing permanent tooth can add significant complications to an otherwise straightforward case. When multiple impacted teeth are present, the case complexity increases further. Developing a treatment sequence, determining appropriate anchorage, and planning and executing sound biomechanics can be a challenge. The following case report illustrates a patient reportedly diagnosed with mild scleroderma as an adolescent. He presented for orthodontic treatment as an adult with multiple retained primary teeth and multiple impacted teeth. Diagnosis, treatment planning, and various methods of managing guided eruption of impacted teeth will be discussed. Following orthodontic treatment that required extraction of multiple primary and permanent teeth as well as exposure and ligation of multiple permanent teeth by an oral surgeon, the patient finished with a significantly improved functional and esthetic result.
Friction of Conventional and Silica-Insert Ceramic Brackets in Various Bracket-Wire Combinations
Authors: Cha Jung-Yul , Kim Kyung-Suk , Hwang Chung-Ju 
Published: May 2007

Abstract
Objective: To compare the level of friction resistance (FR) of conventional and silica-insert ceramic brackets using various bracket-wire combinations and angulations.
Materials and Methods: Four types of ceramic brackets were examined: (1) polycrystalline alumina bracket (PCA-C), (2) polycrystalline alumina bracket with a stainless steel (SS) slot (PCA-M), (3) polycrystalline alumina bracket with a silica layer (PCA-S), and (4) monocrystalline sapphire bracket (MCS). A conventional SS bracket was used as the control. The static and kinetic FR in four bracket-wire angulations (0°, 5°, 10°, and 15°) was examined using SS and β-titanium (β-Ti) orthodontic wires, 0.019 × 0.025 inches in size, under elastic ligature in the dry state.
Results: The FR generated by the PCA-S bracket was significantly lower than that generated with the other ceramic brackets, and was similar to that of the SS bracket. The PCA-S bracket showed the lowest FR with both the SS and the β-Ti wires at zero bracket angulation. The FR to sliding increased rapidly and nonlinearly when the bracket wire angulation was &gt;5°. The PCS-S bracket showed the lowest FR from 5° to 15° of angulation. The MCS bracket demonstrated the highest increase in FR from 0° to 15° of angulation, showing the highest FR at 15° of angulation.
Conclusion: PCA-S showed minimal FR among the ceramic brackets, and was comparable to the conventional SS bracket. The silica layer and rounded edges of the ceramic slot lowered FR considerably.