bluuebunny/crossref_metadata_2025 huggingface dataset:
Rectosigmoid tumours: should we continue sitting on the fence?
Authors: Bagla N. , Schofield J. B.
Published: August 2007

Rectal cancers are currently defined as tumours below 15 cm from the anal verge on rigid sigmoidoscopy. Clinical trials have used this criterion to select patients for neoadjuvant chemoradiotherapy, but several authors have shown that the distance between the fully peritonealized sigmoid colon and the anal canal varies significantly between individuals. A fixed anatomical landmark would be a more reliable and reproducible method of demarcating the junction between the colon and the rectum. The distinction between rectal and sigmoid colon cancers is of particular importance as treatment protocols for rectal cancer management often involve neoadjuvant treatment in contrast to colonic cancers, so it is vital to get the anatomy right. As all rectal cancers are now assessed preoperatively by MRI, the use of a bony landmark is possible. We postulate that the fixed landmark to define the upper limit of the rectum should be the sacral promontory.
Market Reform and Infrastructure Development in Transition Economies
Authors: Feinberg Robert M. , Meurs Mieke
Published: August 2007

This paper analyzes the determinants of investments in physical infrastructure over the first decade of market reform in Central and Eastern Europe and other former Soviet economies. Both market and political reform would be expected to have an impact on the level of infrastructure, but the relationship will likely differ for infrastructure which remains dependent on the public sector and that which becomes more dependent on private investment after such reforms. Results for a large cross section of transition economies show that market reform has had a positive impact on both traditional and newer types of infrastructure, with a stronger impact on the newer types which are more likely to be market‐derived. The findings also suggest that market reform is more likely to push investors to develop infrastructure when political and market reforms are accomplished in tandem.
Trade and Endogenous Formation of Regions in a Developing Country
Authors: Gries Thomas , Naude Wim
Published: August 2007

The authors present a model of regional catching‐up and development without scale effects. Regional growth is driven by technological imitation which is determined by positive externalities from international trade, the regions’ geography, and regional institutions. For the two regions considered, factor endowments are immobile land and human capital which is perfectly mobile between the two regions. Endogenous formation of regions is analyzed by introducing a non‐symmetric decrease in international transaction costs, reflecting the different geography and institutions in the two regions. Using panel data from 354 South African magisterial districts over the period 1996 to 2000, we find that geography is important in explaining trade patterns. As predicted, regions that are larger in terms of economic size, with good foreign market access and know‐how of foreign markets, competitive transport costs and a good local institutional support framework will be more successful in exporting manufactured goods than other regions.
More Control, Less Conflict? Job Demand–Control, Gender and Work–Family Conflict
Authors: Grönlund Anne
Published: August 2007

The connection between working hours and work‐to‐family conflict has been established in a number of studies. However, it seems what is important is not only the quantity of work but also its quality, as captured by the job demand–control model. Survey data from 800 Swedish employees show that job demands spill over negatively into family life, while job control reduces work‐to‐family conflict. Interestingly, women in jobs with high demands and high control — regarded as the prototype for modern, flexible work life — do not experience more work‐to‐family conflict than men, even when working the same hours.
Recruiting, paying and training 16‐ and 17‐year‐old school leavers
Authors: Heyes Jason
Published: August 2007

This article examines firms' pay and employment practices in respect of school leavers aged 16 and 17. The focus is on the manufacturing, hospitality, construction, hairdressing and retail sectors, which are notable for employing relatively large numbers of young workers. Drawing on findings from a postal questionnaire survey of managers and interview data from 28 organisations, the article explores the reasons why firms choose to employ school leavers, the types of jobs that they are considered for and the pay and training they receive. The article also examines the considerations that influence employers' pay practices and the relationship between training activity and average wage levels.
Why is there not more ‘annualised hours’ working in Britain?
Authors: Arrowsmith James
Published: August 2007

Annualised hours (AH) contracts offer employers greater control over working time at lower cost. These efficiency gains may also be shared with workers in terms of pay or time off work. Yet AH remains relatively rare in the UK. Though under‐researched, one explanation is that AH normally requires collective bargaining, which is disappearing across most of the private sector, and often high‐trust employment relations, which is in still shorter supply.
Interest formation in greenfield union organising campaigns
Authors: Simms Melanie
Published: August 2007

This article examines the processes by which unions come to express the interests of workers during organising campaigns. Evidence from five longitudinal cases shows the central importance of officials and organisers. Three key reasons for this are explored: the need for expert knowledge in organising campaigns, the fact that officials and organisers are well placed to identify and to construct common interests among a diversity of interest groups, and the fact that the training they receive explicitly encourages this role. Furthermore, it is argued that this helps explain some of the difficulties observed in organising campaigns specifically; the limitations of campaigns that primarily focus at workplace level, and the relatively narrow definition of collective interests that this approach encourages.
Low-Dose Gabapentin in Treatment of High-Altitude Headache
Authors: Jafarian S , Gorouhi F , Salimi S , Lotfi J
Published: August 2007

Headache is the most prevalent symptom of acute mountain sickness. We conducted a pilot clinical trial at an altitude of 3500 m to evaluate the efficacy of gabapentin in treatment of high-altitude headache (HAH). Twenty-four adult HAH patients (10 female, 14 male; age 18–50 years) were randomly assigned to receive either 300 mg of gabapentin capsule or identical placebo. After 1 h the presence of HAH and need to receive supplementary analgesic were assessed. The duration of the HAH-free phase after taking additional analgesic was also registered. Four patients in the gabapentin group asked for additional analgesics, whereas nine placebo recipients did not find primary medication satisfactory after the first hour of treatment ( P = 0.04). The mean HAH-free period was 17.10 h in the gabapentin group, which was significantly higher than in the placebo group with a mean of 10.08 h ( P = 0.02). This preliminary observation indicates that gabapentin is effective in treatment and alleviation of HAH.
Mothers’ Satisfaction with a Home Based Early Intervention Programme for Children with ASD
Authors: Rodger Sylvia , Keen Deb , Braithwaite Michelle , Cook Shannon
Published: August 2007

Background  Early intervention services adopting a family‐centred approach are considered important for ensuring parent satisfaction. This study investigated the satisfaction of two mothers with an early intervention programme for young children with autistic spectrum disorder.

Materials and Methods  While 16 mother–child dyads participated in a larger study, two mothers who reported considerably lower satisfaction with the programme than the rest of the mothers were the focus of this paper. Using descriptive case studies, various child, parent and service delivery factors that may have influenced satisfaction are described.

Results  Child and parent factors that may have lessened satisfaction for these two mothers included the child’s lack of improvement, child’s goal performance post‐intervention, parenting stress and decreased parenting competence. Both mothers also had decreased perceptions of the family‐centredness of the service and expressed difficulties with establishing collaborative partnerships.

Conclusion  This paper proposes that parental satisfaction may be influenced by numerous factors relating to the child, parent and service. Relationships with service providers appear to be particularly important.
Heterogeneity of fiber characteristics in the rat masseter and digastric muscles
Authors: Sano R. , Tanaka E. , Korfage J. A. M. , Langenbach G. E. J. , Kawai Nobuhiko , Van Eijden T. M. G. J. , Tanne K.
Published: August 2007

The functional requirements in muscle use are related to the fiber type composition of the muscles and the cross‐sectional area of the individual fibers. We investigated the heterogeneity in the fiber type composition and fiber cross‐sectional area in two muscles with an opposing function, namely the digastric and masseter muscles (n = 5 for each muscle) of adult male rats, by means of immunohistochemical staining according to their myosin heavy chain (MyHC) content. The digastric and masseter muscles were taken from Wistar strain male rats 10 weeks old. In the masseter six predefined sample locations were examined; in the digastric four. Most regions showed dominant proportions of type IIA and IIX fibers. However, both muscles also revealed a regional heterogeneity in their fiber type distribution. In the digastric, type I fibers were detected only at the central and deep areas of the anterior and posterior belly, respectively. Meanwhile, the peripheral area of the anterior belly contained a higher proportion of type IIB fibers. In the masseter, the type I fibers were absent. In the superficial masseter the distribution of IIA and IIB fibers was significantly different between the superior and inferior regions. In the deep masseter, regional differences were observed among all four examined areas, of which the posterolateral region contained the highest proportion of type IIB fibers. The cross‐sectional areas of type IIB fibers were always the largest, followed by the type IIX and IIA fibers. Only a few differences in cross‐sectional area of corresponding fiber types were detected between the various sites. In conclusion, the masseter and digastric muscles showed an obvious heterogeneity of fiber type composition and fiber cross‐sectional area. Their heterogeneity reflects the complex role of the both muscles during function. This detailed description of the fiber type composition can serve as a reference for future studies examining the muscular adaptations after the onset of various diseases in the masticatory system.
Treatment of canine mast cell tumours with vinblastine, cyclophosphamide and prednisone: 35 cases (1997–2004)
Authors: Camps‐Palau M. A. , Leibman N. F. , Elmslie R. , Lana S. E. , Plaza S. , McKnight J. A. , Risbon R. , Bergman P. J.
Published: August 2007

The purpose of this retrospective study was to determine the efficacy and toxicity of a combined protocol of vinblastine, cyclophosphamide and prednisone (VCP) in 35 dogs with mast cell tumours (MCTs). Eleven dogs had measurable disease (group 1) and 24 dogs had incompletely excised MCT or were at high risk for metastasis (group 2). Five patients in group 1 achieved complete response, two partial responses, two stable diseases and two progressive diseases. The median progression‐free survival time (PFST) for group 1 and 2 dogs was 74 and 865 days, respectively. The median overall survival time (OST) for group 1 and 2 dogs was 145 and >2092 days, respectively. Significant negative multivariate prognostic factors included macroscopic disease and reduced vinblastine (VBL) treatments for PFST, and presence of MCT in bone marrow analysis, Patnaik grade III MCT and reduced VBL treatments for OST. Toxicity was infrequent and self‐limiting. This study suggests that the VCP protocol should be considered as an option in the treatment of MCT in dogs.
Quantification of plasma DNA as a prognostic indicator in canine lymphoid neoplasia
Authors: Schaefer D. M. W. , Forman M. A. , Kisseberth W. C. , Lehman A. M. , Kelbick N. T. , Harper P. , Rush L. J.
Published: August 2007

Dogs have a similar incidence of spontaneous cancers as people, and a noninvasive test to monitor disease status in dogs would be of great value. Humans with cancer often have increased levels of cell‐free circulating DNA in their plasma, which has shown promise for diagnosis, prognosis and detection of residual disease. We hypothesized that dogs with cancer have increased circulating DNA compared with healthy dogs or dogs with non‐neoplastic diseases. Plasma DNA was measured in 40 healthy dogs, 20 dogs with non‐neoplastic diseases and 80 dogs with cancer. The reference interval for plasma DNA in healthy dogs was 1–15 ng mL−1. Dogs with lymphoma and lymphoid leukaemia had significantly higher concentrations (range: 0–91 ng mL−1, P < 0.0001). Antigen receptor rearrangement assays suggest that plasma DNA had the same clonality as the primary lymphoid tumours. Dogs with lymphoid neoplasia and plasma DNA >25 ng mL−1 had shorter remission times than those with < 25 ng mL−1 (P= 0.0116). In contrast to humans, where increased plasma DNA is seen in many diseases, dogs with nonlymphoid malignancies and non‐neoplastic diseases had plasma DNA concentrations similar to healthy dogs. This study shows that a portion of dogs with lymphoid neoplasia have increased tumour‐derived plasma DNA, which serves as a negative prognostic indicator.
Veterinary cancer registries in companion animal cancer: a review
Authors: Brønden L. B. , Flagstad A. , Kristensen A. T.
Published: August 2007

Current and prior veterinary cancer registries are few in number and scattered. Different inclusion criteria, dissimilar collection methods and variable reference population estimation methods pose obstacles in the comparisons between veterinary and human cancer registries. Veterinary cancer registries have yielded information on the risk and incidence of different cancer types in certain breeds and geographical regions, as well as provided information on genetic and environmental risk factors in some cancers. The objective of this article is to review the prior and current veterinary cancer registries, the information they have contributed and to discuss different issues relating to their structure including inclusion criteria, study populations, reference populations utilized in evaluations, recorded variables and the outcome from these.
Microstructure, Piezoelectric, and Ferroelectric Properties of Bi2O3‐Added (K0.5Na0.5)NbO3 Lead‐Free Ceramics
Authors: Du Hongliang , Liu Daijun , Tang Fusheng , Zhu Dongmei , Zhou Wancheng , Qu Shaobo
Published: August 2007

Lead‐free piezoelectric (K0.5Na0.5)NbO3–x wt% Bi2O3 ceramics have been synthesized by an ordinary sintering technique. The addition of Bi2O3 increases the melting point of the system and improves the sintering temperature of (K0.5Na0.5)NbO3 ceramics. All samples show a pure perovskite phase with a typical orthorhombic symmetry when the Bi2O3 content <0.7 wt%. The phase transition temperature of orthorhombic–tetragonal (TO−T) and tetragonal–cubic (TC) slightly decreased when a small amount of Bi2O3 was added. The remnant polarization Pr increased and the coercive field Ec decreased with increasing addition of Bi2O3. The piezoelectric properties of (K0.5Na0.5)NbO3 ceramics increased when a small amount of Bi2O3 was added. The optimum piezoelectric properties are d33=140 pC/N, kp=0.46, Qm=167, and TC=410°C for (K0.5Na0.5)NbO3–0.5 wt% Bi2O3 ceramics.
Influence of Ag on the Composition and Electromagnetic Properties of Low‐Temperature Cofired Hexaferrites
Authors: Lisjak Darja , Drofenik Miha
Published: August 2007

We have studied the compatibility of Ag and (Co,Cu)Z‐hexaferrite with the composition Ba3Co1.4Cu0.6Fe24O41 (Z). In order to do this, the (Co,Cu)Z‐hexaferrite was cofired with various amounts of Ag at 900°C. The degradation of the (Co,Cu)Z‐hexaferrite to Y‐ and U‐hexaferrite occurred during the cofiring and was confirmed by X‐ray diffraction as well as by thermomagnetic measurements. The permeability and permittivity of the cofired ceramics were measured in the range 1 MHz to 10 GHz. For the (Co,Cu)Z‐hexaferrite, both these properties were significantly influenced by the Ag when the amount of Ag exceeded a minimum of 4.5 wt%. The influence of the Ag and the degradation of the (Co,Cu)Z‐hexaferrite on the permeability were evaluated using the Bruggeman effective media theory.
Structure Development of NiO–YSZ Oxide Mixtures in Simulated Citrate–Nitrate Combustion Synthesis
Authors: Marinšek Marjan , Gomilšek Jana Padežnik , Arčon Iztok , Čeh Miran , Kodre Alojz , Maček Jadran
Published: August 2007

Yttria‐stabilized zirconia (NiO/YSZ) composites were prepared by the modified citrate–nitrate combustion synthesis. The citrate–nitrate combustion proceeded through several consecutive steps. Evolution of structure in the system and its changes were followed up by thermogravimetry‐differential scanning calorimetry, X‐ray powder diffraction, extended X‐ray absorption fine structure, and high resolution transmission electron microscopy analyses of intermediate products prepared at distinct temperatures that correspond to different stages of the combustion process. It was shown that the crystalline structure developed gradually, first with crystallization of nano‐sized NiO particles (400°–700°C), which was followed by crystallization of YSZ (800°–900°C). The final composite material after heat treatment at 1100°C comprised of nano‐crystals with an average size of 6.5±2 nm.
Effect of Albumin on the Growth Characteristics of Hydroxyapatite Coatings on Alumina Substrates
Authors: Chakraborty Jui , Chatterjee Saradiya , Sinha Mithlesh K. , Basu Debabrata
Published: August 2007

A potent biomolecule, egg albumin (EA), has been used in the biomimetic coating of hydroxyapatite (HAp) on α‐Al2O3 substrate. The same experiment was repeated without using EA and the results have been compared. In both cases, the substrates were incubated up to 6 days in SBF (simulated body fluid) at 37°C with a periodic replacement by freshly prepared SBF at 48‐h intervals. The presence of EA influenced the growth and morphology of HAp crystals. Without EA, the HAp coating comprises irregular‐shaped, serrated‐edged plates whereas with EA, thick and regular‐edged HAp crystal plates were observed on the α‐Al2O3 substrate.
Giant Permittivity of a Bismuth Zinc Niobate–Silver Composite
Authors: George Sumesh , James Jose , Sebastian Mailadil Thomas
Published: August 2007

Bismuth zinc niobate–Silver (BZN–Ag) composites were prepared by the solid‐state ceramic route. The sintering temperature of BZN–Ag composites was lowered to 850°C/2 h. The structure and surface morphology of the composites were investigated using X‐ray diffraction and optical microscope. The dielectric and conducting properties of the composites were systematically investigated with the volume fraction of silver in the frequency range from 1 KHz to 1 MHz. The dielectric constant of the composite increases with the silver content and is in good agreement with the power law below the percolation limit. Addition of 0.14 volume fraction of silver increases the dielectric constant of BZN+2 wt% B2O3 from 150 to 2350 at 1 MHz. However, 15 volume percentage of silver loading results in a large permittivity of (ɛr)≈105 with a low dielectric loss (tan δ≈10−2) at 1 MHz. Subsequent increase in silver loading decreases the dielectric constant. The BZN–B2O3–Ag composite with large permittivity may find applications in electromechanical and tunable devices.
Effects of Melting Temperature on the Broadband Infrared Luminescence of Bi‐Doped and Bi/Dy Co‐Doped Chalcohalide Glasses
Authors: Yang Guang , Chen Danping , Ren Jing , Xu Yingsheng , Zeng Huidan , Yang Yunxia , Chen Guorong
Published: August 2007

Bismuth (Bi)‐doped and Bi/Dy co‐doped chalcohalide glasses are investigated as promising materials for amplifiers in optical communication. The samples synthesized at lower melting temperatures (MTs) are characterized by more intensified infrared emissions. With respect to the redox process of a liquid mixture at different MTs, we attribute an emission at 1230 nm to low‐valent Bi ions. The lower MT favors the formation of LVB ions, i.e. Bi+ or Bi2+, while the higher MT promotes the production of higher‐valent Bi ions Bi3+. An enhanced broadband infrared luminescence with the full‐width at half‐maximum over 200 nm is achieved from the present Bi/Dy co‐doped chalcohalide glasses.
The association between maternal periodontitis and low birth weight infants among Malay women
Authors: Saddki Norkhafizah , Bachok Norsa'adah , Hussain Nik Hazlina Nik , Zainudin Siti Lailatul Akmar , Sosroseno Wihaskoro
Published: August 2007

Abstract –  Objectives:  Maternal periodontitis has been suggested as one of the risk factors for low birth weight (LBW) infants. The objective of this study was to determine the association between maternal periodontitis and LBW infants among Malay women.

Methods:  Screening periodontal examinations were carried out on all eligible Malay pregnant women in the second trimester of pregnancy attending two randomly selected community maternal and child health clinics in Kota Bharu, Kelantan. Patients with four or more sites with pocket depth 4 mm or higher, and clinical attachment loss 3 mm or higher at the same site with presence of bleeding on probing were diagnosed as having periodontitis in this study. Using this definition, systematic random sampling was utilized for selection of 250 subjects for each exposed and non‐exposed group. Of 500 subjects enrolled in the study, 28 (5.6%) were either dropped or lost to follow‐up. Of the remaining 472 subjects, 232 with periodontitis were in the exposed group and 240 with healthy periodontium were in the nonexposed group.

Results:  The incidence of LBW was 14.2% (95% CI: 9.70–18.75) in women with periodontitis, and 3.3% (95% CI: 1.05–5.62) in women without periodontitis. The relative risk of having LBW infants was 4.27 times higher for women with periodontitis compared with those without periodontitis (95% CI: 2.01–9.04). After adjustment for potential confounders using multiple logistic regression analysis, significant association was found between maternal periodontitis and LBW (OR = 3.84; 95% CI: 1.34–11.05).

Conclusion:  The results of this study provide additional evidence that pregnant women with periodontitis are at a significantly higher risk of delivering LBW infants.
Caries status and overweight in 2‐ to 18‐year‐old US children: findings from national surveys
Authors: Kopycka‐Kedzierawski D. T. , Auinger P. , Billings R. J. , Weitzman M.
Published: August 2007

Abstract –  Background:  The prevalence of overweight children in the United States continues to increase.

Objectives:  To examine the relationship between being overweight and caries in primary and permanent dentition in a nationally representative sample of children.

Methods:  Data from the NHANES III (1988–1994) were analyzed using logistic regression and controlling for potential confounders for 10 180 children 2–18 years of age and from the NHANES 1999–2002 for 7568 children 2–18 years of age.

Results:  For children 2–5 years of age, there was no difference in caries experience among normal weight, at risk for overweight or overweight children for NHANES III and for NHANES 1999–2002. For children 6–11 years of age (NHANES III), at risk for overweight and overweight children were less likely to have caries experience in the primary dentition than normal weight children; overweight children were less likely to have caries experience in the permanent dentition than normal weight children. For children 12–18 years of age (NHANES III), overweight children were less likely to have caries experience in the permanent dentition than normal weight children. For children 6–11 years of age and 12–18 years of age (NHANES 1999–2002), there was no difference in having caries experience among normal, at risk for overweight and overweight children.

Conclusions:  The data from NHANES III and NHANES 1999–2002 provide no evidence to suggest that overweight children are at an increased risk for dental caries. Although no differences in caries rates by weight were found in younger children, interestingly results from NHANES III suggest that being overweight may be associated with decreased rates of caries in older children.
Factors associated with prevalence and severity of caries experience in preschool children
Authors: Declerck Dominique , Leroy Roos , Martens Luc , Lesaffre Emmanuel , Garcia‐Zattera Maria‐José , Broucke Stephan Vanden , Debyser Martine , Hoppenbrouwers Karel
Published: August 2007

Abstract –  Objectives:  The aim of the present study was to examine the prevalence and severity of caries experience in the primary dentition of preschool children and to assess the association of disease distribution with oral hygiene levels, reported oral health behaviours and socio‐demographic factors.

Methods:  Study samples comprised 1250 3‐year‐old and 1283 5‐year‐old pre‐school children from four distinct geographical areas in Flanders. Information on oral hygiene and dietary habits, oral health behaviours and socio‐demographic variables was collected using questionnaires completed by the parents. Clinical examinations were performed using standardized criteria. Caries experience was recorded at the level of cavitation (d3 level). Simple as well as multivariable logistic regression analyses were performed in order to identify factors associated with prevalence and severity of caries experience.

Results:  Visible plaque was present in 31% of 3‐year‐olds and 37% of 5‐year‐olds. In 3‐year‐olds, 7% presented with caries experience while this was the case in 31% of 5‐year‐olds. Multivariable logistic regression revealed significant associations, in 3‐year‐olds, of caries experience with presence of dental plaque (OR = 7.93; 95% CI: 2.56–24.55) and reported consumption of sugared drinks at night (OR = 7.96; 95% CI: 1.57–40.51). In 5‐year‐olds, significant associations were seen with age (OR = 7.79; 95% CI: 2.38–25.43), gender (OR = 0.37 with 95% CI: 0.19–0.71 for girls), presence of visible dental plaque (OR = 3.36; 95% CI: 1.64–6.89) and reported habit of having sugar‐containing drinks in between meals (OR = 2.60 with 95% CI: 1.16–5.84 and OR = 3.18 with 95% CI: 1.39–7.28, respectively for 1×/day and > 1×/day versus not every day). In 5‐year‐olds with caries experience (30.8% of total sample), the severity of disease was further analysed (d3mft between 1 and 4 versus d3mft 5 or higher). Multivariable analyses showed a significant association with gender [girls more likely to have higher disease levels; OR = 4.67 (95% CI: 1.65–13.21)] and with presence of plaque (OR = 3.91 with 95% CI: 1.23–12.42).

Conclusions:  Presence of visible plaque accumulation and reported consumption of sugared drinks were associated with prevalence of caries experience in Flemish preschool children. Severity of disease was associated with gender and with presence of plaque. Results underline the importance of plaque control and diet management from very young age on.
Molecular analysis in a patient with severe factor VII deficiency and an inhibitor: report of a novel mutation (S103G)
Authors: Pruthi Rajiv K. , Rodriguez Vilmarie , Allen Cory , Slaby Jeffrey A. , Schmidt Kirstin A. , Plumhoff Elizabeth A.
Published: August 2007

Congenital factor VII (FVII) deficiency is an autosomal recessive bleeding disorder with variable phenotypic correlation between FVII activity and bleeding risk. We report a novel mutation of the FVII gene that creates the amino acid change Ser 103 to Gly, which resulted in severe FVII deficiency with reduced FVII antigen. This mutation in the heterozygous form was also present in a mildly affected, unrelated patient. We also report on the natural history of an FVII inhibitor in the patient with severe FVII deficiency.
Molecular Characterization of Plant Prevacuolar and Endosomal Compartments
Authors: Lam Sheung Kwan , Tse Yu Chung , Miao Yansong , Li Hong‐Ye , Wang Junqi , Lo Sze Wan , Jiang Liwen
Published: August 2007

Prevacuolar compartments (PVCs) and endosomal compartments are membrane‐bound organelles mediating protein traffic to vacuoles in the secretory and endocytic pathways of plant cells. Over the years, great progress has been made towards our understanding in these two compartments in plant cells. In this review, we will summarize our contributions toward the identification and characterization of plant prevacuolar and endosomal compartments. Our studies will serve as important steps in future molecular characterization of PVC biogenesis and PVC‐mediated protein trafficking in plant cells.
Cytoskeleton and Early Development in Fucoid Algae
Authors: Bisgrove Sherryl R.
Published: August 2007

Cell polarization and asymmetric cell divisions play important roles during development in many multicellular eukaryotes. Fucoid algae have a long history as models for studying early developmental processes, probably because of the ease with which zygotes can be observed and manipulated in the laboratory. This review discusses cell polarization and asymmetric cell divisions in fucoid algal zygotes with an emphasis on the roles played by the cytoskeleton.
Primary Cell Wall Structure in the Evolution of Land Plants
Authors: Nothnagel Alex L. , Nothnagel Eugene A.
Published: August 2007

Investigation of the primary cell walls of lower plants improves our understanding of the cell biology of these organisms but also has the potential to improve our understanding of cell wall structure and function in angiosperms that evolved from lower plants. Cell walls were prepared from eight species, ranging from a moss to advanced gymnosperms, and subjected to sequential chemical extraction to separate the main polysaccharide fractions. The glycosyl compositions of these fractions were then determined by gas chromatography. The results were compared among the eight plants and among data from related studies reported in the existing published reports to identify structural features that have been either highly conserved or clearly modified during evolution. Among the highly conserved features are the presence of a cellulose framework, the presence of certain hemicelluloses such as xyloglucan, and the presence of rhamnogalacturonan II, a domain in pectic polysaccharides. Among the modified features are the abundance of mannosyl‐containing hemicelluloses and the presence of methylated sugars.
Genetic Analyses of Meiotic Recombination in Arabidopsis
Authors: Wijeratne Asela J. , Ma Hong
Published: August 2007

Meiosis is essential for sexual reproduction and recombination is a critical step required for normal meiosis. Understanding the underlying molecular mechanisms that regulate recombination is important for medical, agricultural and ecological reasons. Readily available molecular and cytological tools make Arabidopsis an excellent system to study meiosis. Here we review recent developments in molecular genetic analyses on meiotic recombination. These include studies on plant homologs of yeast and animal genes, as well as novel genes that were first identified in plants. The characterizations of these genes have demonstrated essential functions from the initiation of recombination by double‐strand breaks to repair of such breaks, from the formation of double‐Holliday junctions to possible resolution of these junctions, both of which are critical for crossover formation. The recent advances have ushered a new era in plant meiosis, in which the combination of genetics, genomics, and molecular cytology can uncover important gene functions.
Mechanisms of Organelle Inheritance in Dividing Plant Cells
Authors: Sheahan Michael B , Rose Ray J , McCurdy David W
Published: August 2007

Organelles form essential compartments of all eukaryotic cells. Mechanisms that ensure the unbiased inheritance of organelles during cell division are therefore necessary to maintain the viability of future cell generations. Although inheritance of organelles represents a fundamental component of the cell cycle, surprisingly little is known about the underlying mechanisms that facilitate unbiased organelle inheritance. Evidence from a select number of studies, however, indicates that ordered organelle inheritance strategies exist in dividing cells of higher plants. The basic requirement for unbiased organelle inheritance is the duplication of organelle volume and distribution of the resulting organelle populations in a manner that facilitates unbiased partitioning of the organelle population to each daughter cell. Often, partitioning strategies are specific to the organelle, being influenced by the functional requirements of the organelle and whether the cells are mitotically active or re‐entering into the cell cycle. Organelle partitioning mechanisms frequently depend on interactions with either the actin or microtubule cytoskeleton. In this focused review, we attempt to summarize key findings regarding organelle partitioning strategies in dividing cells of higher plants. We particularly concentrate on the role of the cytoskeleton in mediating unbiased organelle partitioning.
A Putative Calcium‐Permeable Cyclic Nucleotide‐Gated Channel, CNGC18, Regulates Polarized Pollen Tube Growth
Authors: Chang Fang , Yan An , Zhao Li‐Na , Wu Wei‐Hua , Yang Zhenbiao
Published: August 2007

A tip‐focused Ca2+ gradient is tightly coupled to polarized pollen tube growth, and tip‐localized influxes of extracellular Ca2+ are required for this process. However the molecular identity and regulation of the potential Ca2+ channels remains elusive. The present study has implicated CNGC18 (cyclic nucleotide‐gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca2+]ex). CNGC18‐yellow fluorescence protein (YFP) was preferentially localized to the apparent post‐Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes. The PM localization was affected by tip‐localized ROP1 signaling. Expression of wild type
ROP1 or an active form of ROP1 enhanced CNGC18‐YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator) blocked the PM localization. These results support a role for PM‐localized CNGC18 in the regulation of polarized pollen tube growth through its potential function in the modulation of calcium influxes.
The Pleiomorphic Plant MTOC: An Evolutionary Perspective
Authors: Brown Roy C. , Lemmon Betty E.
Published: August 2007

γ‐Tubulin is an essential component of the microtubule organizing center (MTOC) responsible for nucleating microtubules in both plants and animals. Whereas γ‐tubulin is tightly associated with centrosomes that are inheritable organelles in cells of animals and most algae, it appears at different times and places to organize the myriad specialized microtubule systems that characterize plant cells. We have traced the distribution of γ‐tubulin through the cell cycle in representative land plants (embryophytes) and herein present data that have led to a concept of the pleiomorphic and migratory MTOC. The many forms of the plant MTOC at spindle organization constitute pleiomorphism, and stage‐specific “migration” is suggested by the consistent pattern of redistribution of γ‐tubulin during mitosis. Mitotic spindles may be organized at centriolar centrosomes (only in final divisions of spermatogenesis), polar organizers (POs), plastid MTOCs, or nuclear envelope MTOCs (NE‐MTOCs). In all cases, with the possible exception of centrosomes in spermatogenesis, the γ‐tubulin migrates to broad polar regions and along the spindle fibers, even when it is initially a discrete polar entity. At anaphase it moves poleward, and subsequently migrates from polar regions (distal nuclear surfaces) into the interzone (proximal nuclear surfaces) where interzonal microtubule arrays and phragmoplasts are organized. Following cytokinesis, γ‐tubulin becomes associated with nuclear envelopes and organizes radial microtubule systems (RMSs). These may exist only briefly, before establishment of hoop‐like cortical arrays in vegetative tissues, or they may be characteristic of interphase in syncytial systems where they serve to organize the common cytoplasm into nuclear cytoplasmic domains (NCDs).
Transformations of the Pleiomorphic Plant MTOC during Sporogenesis in the Hepatic Marchantia polymorpha
Authors: Brown Roy C. , Lemmon Betty E. , Shimamura Masaki
Published: August 2007

Sporogenesis in the hepatic Marchantia polymorpha L. provides an outstanding example of the pleiomorphic nature of the plant microtubule organizing center (MTOC). Microtubules are nucleated from γ‐tubulin in MTOCs that change form during mitosis and meiosis. Following entry of cells into the reproductive pathway of sporogenesis, successive rounds of mitosis give rise to packets of 4–16 sporocytes. Mitotic spindles are organized at discrete polar organizers (POs), a type of MTOC that is unique to this group of early divergent land plants. An abrupt and radical transformation in microtubule organization occurs when sporocytes enter meiosis: POs are lost and γ‐tubulin is closely associated with surfaces of two large elongated plastids that subsequently divide into four. Migration of the four plastid MTOCs into a tetrahedral arrangement establishes the future spore domains and the division polarity of meiosis. As is typical of many bryophytes, cones of microtubules from the four plastid MTOCs initiate a quadripolar microtubule system (QMS) in meiotic prophase. At this point a transformation in the organization of the MTOCs occurs. The γ‐tubulin detaches from plastids and forms a diffuse spheroidal pole in each of the spore domains. The plastids, which are no longer MTOCs, continue to divide. The diffuse MTOCs continue to nucleate cones of microtubules during transformation of the QMS to a bipolar spindle. Following meiosis I, γ‐tubulin is associated with nuclear envelopes, and the spindles of meiosis II are organized from diffuse MTOCs at the tetrad poles. At simultaneous cytokinesis, radial microtubule systems are organized at nuclear envelope MTOCs in each of the tetrad members.
Control of Directional Macromolecular Trafficking Across Specific Cellular Boundaries: A Key to Integrative Plant Biology
Authors: Ding Biao , Itaya Asuka
Published: August 2007

There is now solid evidence that cell‐to‐cell trafficking of certain proteins and RNAs plays a critical role in trans‐cellular regulation of gene expression to coordinate cellular differentiation and development. Such trafficking also is critical for viral infection and plant defense. The mechanisms of trafficking remain poorly understood. Although some proteins may move between cells by diffusion, many proteins and RNAs move in a highly regulated fashion. Regulation is likely achieved through interactions between distinct protein or RNA motifs and cellular factors. Some motifs and factors have been identified. One of the major focuses for future studies is to identify all motifs and their cognate factors and further elucidate their roles in trafficking between specific cells. With increasing information from such studies, we should be able to develop an understanding of the mechanisms that regulate trafficking of various proteins and RNAs across all and specific cellular boundaries. On the basis of such mechanistic knowledge, we can further investigate how the trafficking machinery has evolved to regulate developmental and physiological processes in a plant, how pathogens have co‐evolved to use this machinery for systemic spread in a plant, and how plants use this machinery for counter‐ defense.
The Katanin Microtubule Severing Protein in Plants
Authors: Burk David H. , Zhong Ruiqin , Ye Zheng‐Hua
Published: August 2007

Katanin is a heterodimeric microtubule (MT) severing protein that uses energy from ATP hydrolysis to generate internal breaks along MTs. Katanin p60, one of the two subunits, possesses ATPase and MT‐binding/severing activities, and the p 80 subunit is responsible for targeting of katanin to certain subcellular locations. In animals, katanin plays an important role in the release of MTs from their nucleation sites in the centrosome. It is also involved in severing MTs into smaller fragments which can serve as templates for further polymerization to increase MT number during meiotic and mitotic spindle assembly. Katanin homologs are present in a wide variety of plant species. The Arabidopsis katanin homolog has been shown to possess ATP‐dependent MT severing activity in vitro and exhibit a punctate localization pattern at the cell cortex and the perinuclear region. Disruption of katanin functions by genetic mutations causes a delay in the disappearance of the perinuclear MT array and results in an aberrant organization of cortical MTs in elongating cells. Consequently, katanin mutations lead to defects in cell elongation, cellulose microfibril deposition, and hormonal responses. Studies of katanin in plants provide new insights into our understanding of its roles in cellular functions.
How do Plants Organize Microtubules Without a Centrosome?
Authors: Murata Takashi , Tanahashi Takako , Nishiyama Tomoaki , Yamaguchi Kazuo , Hasebe Mitsuyasu
Published: August 2007

A microtubule nucleates from a γ‐tubulin complex, which consists of γ‐tubulin, proteins from the SPC97/SPC98 family, and the WD40 motif protein GCP‐WD. We analyzed the phylogenetic relationships of the genes encoding these proteins and found that the components of this complex are widely conserved among land plants and other eukaryotes. By contrast, the interphase and mitotic arrays of microtubules in land plants differ from those in other eukaryotes. In the interphase cortical array, the majority of microtubules nucleate on existing microtubules in the absence of conspicuous microtubule organizing centers (MTOCs), such as a centrosome. During mitosis, the spindle also forms in the absence of conspicuous MTOCs. Both poles of the spindle are broad, and branched structures of microtubules called microtubule converging centers form at the poles. In this review, we hypothesize that the microtubule converging centers form via microtubule‐dependent microtubule nucleation, as in the case of the interphase arrays. The evolutionary insights arising from the molecular basis of the diversity in microtubule organization are discussed.
The Villin/Gelsolin/Fragmin Superfamily Proteins in Plants
Authors: Su Hui , Wang Ting , Dong Huaijian , Ren Haiyun
Published: August 2007

The villin/gelsolin/fragmin superfamily is a conserved Ca2+‐dependent family of actin‐regulating proteins that is widely present both in mammalian and non‐mammalian organisms. They have traditionally been characterized by the same core of three or six tandem gelsolin subdomains. The study in vertebrates and lower eukaryotic cells has revealed that the villin/gelsolin/fragmin superfamily of proteins has versatile functions including severing, capping, nucleating or bundling actin filaments. In plants, encouraging progress has been made in this field of research in recent years. This review will summarize the identified plant homologs of villin/gelsolin/fragmin superfamily, thus providing a basis for reflection on their biochemical activities and functions in plants.
In Silico Identification of Co‐transcribed Core Cell Cycle Regulators and Transcription Factors in Arabidopsis
Authors: Wang Yixing , Yang Ming
Published: August 2007

Regulatory networks involving transcription factors and core cell cycle regulators are expected to play crucial roles in plant growth and development. In this report, we describe the identification of two groups of co‐transcribed core cell cycle regulators and transcription factors via a two‐step in silico screening. The core cell cycle regulators include TARDY ASYNCHRONOUS MEIOSIS (CYCA1;2), CYCB1;1, CYCB2;1, CDKB1;2, and CDKB2;2 while the transcription factors include CURLY LEAF, AINTEGUMENTA, a MYB protein, two Forkhead‐associated domain proteins, and a SCARECROW family protein. Promoter analysis revealed a potential web of cross‐ and self‐regulations among the identified proteins. Because one criterion for screening for these genes is that they are predominantly transcribed in young organs but not in mature organs, these genes are likely to be particularly involved in Arabidopsis organ growth.
Toxicity Profile of Lisdexamfetamine Dimesylate in Three Independent Rat Toxicology Studies
Authors: Krishnan Suma , Montcrief Scott
Published: August 2007

Abstract:  Lisdexamfetamine dimesylate (LDX) is a d‐amphetamine prodrug developed for the treatment of attention‐deficit/hyperactivity disorder. The toxicity profile of orally administered LDX has been evaluated in rats. In an acute study, LDX doses of 60 mg/kg and higher caused increased motor activity. At 1000 mg/kg, one rat died and another was euthanized. In a 7‐day repeat‐dose study, all rats dosed with LDX (14 per dose group for each sex) showed increased activity; 10 male rats and 11 female rats at 300 mg/kg/day and 3 female rats at 100 mg/kg/day were euthanized because of self‐mutilation and 1 male rat at 300 mg/kg/day was found dead. In a 28‐day study, only rats at 80 mg/kg showed signs of self‐mutilation and thin body condition. In both the 7‐ and 28‐day studies, LDX caused significant changes in some blood chemistry parameters (e.g. blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase) and organ weights (e.g. particularly heart, liver, brain, and spleen). Overall, no apparent treatment‐related histopathologic changes were observed. Toxicokinetic assessments indicated that as the dose of LDX was increased, rats were exposed to increasing levels of LDX and d‐amphetamine. The extent of exposure to LDX and d‐amphetamine increased after repeated‐dose in the 28‐day study. The findings of the repeat‐dose studies indicate that the toxicity profile in rats administered LDX orally is comparable to that for d‐amphetamine; however, the apparent lethal dose of LDX in rats is more than five times higher than the LD50 of orally administered d‐amphetamine, supporting a putative protective effect of conjugating amphetamine with lysine.