bluuebunny/crossref_metadata_2025 huggingface dataset:
Ancient Origin of the Tryptophan Operon and the Dynamics of Evolutionary Change
Authors: Xie Gary , Keyhani Nemat O. , Bonner Carol A. , Jensen Roy A.
Published: September 2003

The seven conserved enzymatic domains required for tryptophan (Trp) biosynthesis are encoded in seven genetic regions that are organized differently (whole-pathway operons, multiple partial-pathway operons, and dispersed genes) in prokaryotes. A comparative bioinformatics evaluation of the conservation and organization of the genes of Trp biosynthesis in prokaryotic operons should serve as an excellent model for assessing the feasibility of predicting the evolutionary histories of genes and operons associated with other biochemical pathways. These comparisons should provide a better understanding of possible explanations for differences in operon organization in different organisms at a genomics level. These analyses may also permit identification of some of the prevailing forces that dictated specific gene rearrangements during the course of evolution. Operons concerned with Trp biosynthesis in prokaryotes have been in a dynamic state of flux. Analysis of closely related organisms among the Bacteria at various phylogenetic nodes reveals many examples of operon scission, gene dispersal, gene fusion, gene scrambling, and gene loss from which the direction of evolutionary events can be deduced. Two milestone evolutionary events have been mapped to the 16S rRNA tree of Bacteria, one splitting the operon in two, and the other rejoining it by gene fusion. The Archaea, though less resolved due to a lesser genome representation, appear to exhibit more gene scrambling than the Bacteria. The
trp
operon appears to have been an ancient innovation; it was already present in the common ancestor of Bacteria and Archaea. Although the operon has been subjected, even in recent times, to dynamic changes in gene rearrangement, the ancestral gene order can be deduced with confidence. The evolutionary history of the genes of the pathway is discernible in rough outline as a vertical line of descent, with events of lateral gene transfer or paralogy enriching the analysis as interesting features that can be distinguished. As additional genomes are thoroughly analyzed, an increasingly refined resolution of the sequential evolutionary steps is clearly possible. These comparisons suggest that present-day
trp
operons that possess finely tuned regulatory features are under strong positive selection and are able to resist the disruptive evolutionary events that may be experienced by simpler, poorly regulated operons.
Longevity Regulation inSaccharomyces cerevisiae: Linking Metabolism, Genome Stability, and Heterochromatin
Authors: Bitterman Kevin J. , Medvedik Oliver , Sinclair David A.
Published: September 2003

When it was first proposed that the budding yeast Saccharomyces cerevisiae might serve as a model for human aging in 1959, the suggestion was met with considerable skepticism. Although yeast had proved a valuable model for understanding basic cellular processes in humans, it was difficult to accept that such a simple unicellular organism could provide information about human aging, one of the most complex of biological phenomena. While it is true that causes of aging are likely to be multifarious, there is a growing realization that all eukaryotes possess surprisingly conserved longevity pathways that govern the pace of aging. This realization has come, in part, from studies of S. cerevisiae, which has emerged as a highly informative and respected model for the study of life span regulation. Genomic instability has been identified as a major cause of aging, and over a dozen longevity genes have now been identified that suppress it. Here we present the key discoveries in the yeast-aging field, regarding both the replicative and chronological measures of life span in this organism. We discuss the implications of these findings not only for mammalian longevity but also for other key aspects of cell biology, including cell survival, the relationship between chromatin structure and genome stability, and the effect of internal and external environments on cellular defense pathways. We focus on the regulation of replicative life span, since recent findings have shed considerable light on the mechanisms controlling this process. We also present the specific methods used to study aging and longevity regulation in S. cerevisiae.
Candida albicansSecreted Aspartyl Proteinases in Virulence and Pathogenesis
Authors: Naglik Julian R. , Challacombe Stephen J. , Hube Bernhard
Published: September 2003

Candida albicans is the most common fungal pathogen of humans and has developed an extensive repertoire of putative virulence mechanisms that allows successful colonization and infection of the host under suitable predisposing conditions. Extracellular proteolytic activity plays a central role in Candida pathogenicity and is produced by a family of 10 secreted aspartyl proteinases (Sap proteins). Although the consequences of proteinase secretion during human infections is not precisely known, in vitro, animal, and human studies have implicated the proteinases in C. albicans virulence in one of the following seven ways: (i) correlation between Sap production in vitro and Candida virulence, (ii) degradation of human proteins and structural analysis in determining Sap substrate specificity, (iii) association of Sap production with other virulence processes of C. albicans, (iv) Sap protein production and Sap immune responses in animal and human infections, (v) SAP gene expression during Candida infections, (vi) modulation of C. albicans virulence by aspartyl proteinase inhibitors, and (vii) the use of SAP-disrupted mutants to analyze C. albicans virulence. Sap proteins fulfill a number of specialized functions during the infective process, which include the simple role of digesting molecules for nutrient acquisition, digesting or distorting host cell membranes to facilitate adhesion and tissue invasion, and digesting cells and molecules of the host immune system to avoid or resist antimicrobial attack by the host. We have critically discussed the data relevant to each of these seven criteria, with specific emphasis on how this proteinase family could contribute to Candida virulence and pathogenesis.
Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH
Authors: Cotter Paul D. , Hill Colin
Published: September 2003

Gram-positive bacteria possess a myriad of acid resistance systems that can help them to overcome the challenge posed by different acidic environments. In this review the most common mechanisms are described: i.e., the use of proton pumps, the protection or repair of macromolecules, cell membrane changes, production of alkali, induction of pathways by transcriptional regulators, alteration of metabolism, and the role of cell density and cell signaling. We also discuss the reponses ofListeria monocytogenes,Rhodococcus,Mycobacterium,Clostridium perfringens,Staphylococcus aureus,Bacillus cereus, oral streptococci, and lactic acid bacteria to acidic environments and outline ways in which this knowledge has been or may be used to either aid or prevent bacterial survival in low-pH environments.
Transmembrane Movement of Exogenous Long-Chain Fatty Acids: Proteins, Enzymes, and Vectorial Esterification
Authors: Black Paul N. , DiRusso Concetta C.
Published: September 2003

The processes that govern the regulated transport of long-chain fatty acids across the plasma membrane are quite distinct compared to counterparts involved in the transport of hydrophilic solutes such as sugars and amino acids. These differences stem from the unique physical and chemical properties of long-chain fatty acids. To date, several distinct classes of proteins have been shown to participate in the transport of exogenous long-chain fatty acids across the membrane. More recent work is consistent with the hypothesis that in addition to the role played by proteins in this process, there is a diffusional component which must also be considered. Central to the development of this hypothesis are the appropriate experimental systems, which can be manipulated using the tools of molecular genetics. Escherichia coli and Saccharomyces cerevisiae are ideally suited as model systems to study this process in that both (i) exhibit saturable long-chain fatty acid transport at low ligand concentrations, (ii) have specific membrane-bound and membrane-associated proteins that are components of the transport apparatus, and (iii) can be easily manipulated using the tools of molecular genetics. In both systems, central players in the process of fatty acid transport are fatty acid transport proteins (FadL or Fat1p) and fatty acyl coenzyme A (CoA) synthetase (FACS; fatty acid CoA ligase [AMP forming] [EC 6.2.1.3]). FACS appears to function in concert with FadL (bacteria) or Fat1p (yeast) in the conversion of the free fatty acid to CoA thioesters concomitant with transport, thereby rendering this process unidirectional. This process of trapping transported fatty acids represents one fundamental mechanism operational in the transport of exogenous fatty acids.
Safety in numbers: more walkers and bicyclists, safer walking and bicycling
Authors: Jacobsen P L
Published: September 2003

Objective:To examine the relationship between the numbers of people walking or bicycling and the frequency of collisions between motorists and walkers or bicyclists. The common wisdom holds that the number of collisions varies directly with the amount of walking and bicycling. However, three published analyses of collision rates at specific intersections found a non-linear relationship, such that collisions rates declined with increases in the numbers of people walking or bicycling.

Data:This paper uses five additional data sets (three population level and two time series) to compare the amount of walking or bicycling and the injuries incurring in collisions with motor vehicles.

Results:The likelihood that a given person walking or bicycling will be struck by a motorist varies inversely with the amount of walking or bicycling. This pattern is consistent across communities of varying size, from specific intersections to cities and countries, and across time periods.

Discussion:This result is unexpected. Since it is unlikely that the people walking and bicycling become more cautious if their numbers are larger, it indicates that the behavior of motorists controls the likelihood of collisions with people walking and bicycling. It appears that motorists adjust their behavior in the presence of people walking and bicycling. There is an urgent need for further exploration of the human factors controlling motorist behavior in the presence of people walking and bicycling.

Conclusion:A motorist is less likely to collide with a person walking and bicycling if more people walk or bicycle. Policies that increase the numbers of people walking and bicycling appear to be an effective route to improving the safety of people walking and bicycling.
Trends in hospitalization after injury: older women are displacing young men
Authors: Shinoda-Tagawa T , Clark D E
Published: September 2003

Objective:To evaluate trends in hospitalization after injuries in the USA.

Design:National Hospital Discharge Survey data from 1979 to 2000 were evaluated annually by age group, sex, injury severity score (ISS), length of stay, and discharge destination.

Setting and subjects:National probability sample of hospitalized patients.

Interventions:None.

Main outcome measures:Incidence, duration, outcome, and population based rates of hospital admission after injuries.

Results:The number of young males admitted to hospitals after injuries has decreased dramatically; older females are now the group most frequently admitted. Total days in the hospital have decreased in all age groups, but have declined less in the older population than in the younger population; furthermore, most patients aged 65 and over were formerly discharged home, but now most are discharged to long term care facilities. Overall hospitalization rates after injury have decreased in all age groups, but have declined less in the older population; furthermore, male and female hospitalization rates for serious injury (ISS at least 9, excluding isolated hip fracture) are decreasing in younger age groups while increasing in older age groups.

Conclusions:Older patients comprise a growing proportion of injuries requiring hospitalization. Trauma systems must address this change, and preventing injuries in older people is increasingly important.
Injuries among disabled children: a study from Greece
Authors: Petridou E , Kedikoglou S , Andrie E , Farmakakis T , Tsiga A , Angelopoulos M , Dessypris N , Trichopoulos D
Published: September 2003

Objective:To compare the differential implications of sociodemographic and situational factors on the risk of injury among disabled and non-disabled children.

Design:Data from the Emergency Department Injury Surveillance System (EDISS) were used to compare, in a quasi case-control approach, injured children with or without disability with respect to sociodemographic, event and injury variables, and to estimate adjusted odds ratios for the injury in a disabled rather than a non-disabled child.

Setting:Two teaching hospitals in Athens and two district hospitals in the countryside that participate in the EDISS.

Patients:In the five year period 1996–2000, 110 066 children were recorded with injuries; 251 among them were identified as having a motor/psychomotor or sensory disability before the injury event.

Interventions:None.

Main outcome measures:Mechanism of injury, type of injury, risk-predisposing socioeconomic and environmental variables, odds ratio for injury occurrence.

Results:Falls and brain concussion are proportionally more common among disabled children, whereas upper limb and overexertion injuries are less common among them. Urban environment, migrant status, and cold months are also associated with increased odds for injuries to occur among disabled rather than non-disabled children. The odds ratio for the occurrence of an injury among disabled children increases with increasing age.

Conclusions:The results of the study provide the information for the targeting of trials of preventive measure in disabled children at increased risk of severe injuries.
Community based program to improve firearm storage practices in rural Alaska
Authors: Horn A , Grossman D C , Jones W , Berger L R
Published: September 2003

Objective:To develop and evaluate a pilot program to reduce unauthorized access to firearms by youth by distributing gun safes and trigger locks to households.

Design:Pilot intervention with pre/post-evaluation design.

Setting:Two Alaska Native villages in the Bristol Bay Health Corporation region of southwest Alaska.

Subjects:Forty randomly selected households with two or more guns in the home.

Intervention:Initially, a focus group of community members who owned guns was convened to receive input regarding the acceptability of the distribution procedure for the gun storage devices. One gun safe and one trigger lock were distributed to each of the selected households during December 2000. Village public safety officers assisted with the distribution of the safes and provided gun storage education to participants.

Main outcome measures:Baseline data were collected regarding household gun storage conditions at the time of device distribution. Three months after distribution, unannounced onsite home visits were conducted to identify if residents were using the gun safes and/or trigger locks.

Results:All selected households had at least two guns and 28 (70%) of the 40 households owned more than two guns. At baseline, 85% of homes were found to have unlocked guns in the home and were most often found in the breezeway, bedroom, storage room, or throughout the residence. During the follow up visits, 32 (86%) of the 37 gun safes were found locked with guns inside. In contrast, only 11 (30%) of the 37 trigger locks were found to be in use.

Conclusions:This community based program demonstrated that Alaska Native gun owners accepted and used gun safes when they were installed in their homes, leading to substantial improvements in gun storage practices. Trigger locks were much less likely to be used.
Farm work practices and farm injuries in Colorado
Authors: Stallones L , Beseler C
Published: September 2003

Study objectives:To describe the farm work patterns and the relationship between hours spent working on specific farm tasks and task specific work related injuries among women and men.

Design:A cross sectional survey of farm operators and their spouses in an eight county area of Colorado was conducted. Personal interviews were conducted between 1993 and 1997. Interviews took between 45 minutes to two hours to complete, depending on the complexity of individuals’ personal histories. Farms were selected using stratified random sampling technique.

Setting:Eight counties in Northeastern Colorado representing 47% of agricultural production in the state.

Participants:A total of 301 women and 459 men who were farm residents and involved in farm work were recruited.

Outcome measure:Self reported injuries resulting in medical attention or treatment other than first aid, or inability to do normal work activities, or loss of consciousness, or transfer to another job were assessed in relationship to the specific job task being performed at the time of the injury.

Results:Women were at higher risk for injury than men when involved with other farm chores (rate ratio 8.18). For all other task related injuries, men and women were at similar risk when compared using hours of exposure to the farm tasks.

Conclusion:Farm safety training and injury prevention programs need to include women working on farms.
Nighttime driving, passenger transport, and injury crash rates of young drivers
Authors: Rice T M , Peek-Asa C , Kraus J F
Published: September 2003

Objective:This study examines the association of nighttime driving and the carrying of passengers with the rate of motor vehicle crashes that resulted in severe or fatal injury to young drivers in California before the implementation of a graduated licensing system.

Method:Passenger vehicle drivers aged 16 or 17 involved in injury crashes in California from 1 January 1993 to 30 June 1998 were identified through a police crash database. An induced exposure method was used to estimate driving exposure. Odds ratios for driver injury crashes were estimated with logistic regression.

Results:Driving at night, driving without adult supervision, driving with passengers, using alcohol, being 16, and being male were associated with high rates of driver injury crash.

Conclusions:The injury crash rate for drivers aged 16 or 17 increases during nighttime hours and in the absence of adult supervision, with or without other passengers. Driving between 10 pm and midnight is particularly dangerous for young drivers. Nighttime driving restrictions that begin at 10 pm or earlier and restrictions on carrying passengers at any hour may increase the effectiveness of graduated licensing systems.
Motor vehicle crash fatalities by race/ethnicity in Arizona, 1990–96
Authors: Campos-Outcalt D , Bay C , Dellapena A , Cota M K
Published: September 2003

Objective:To compare rates of motor vehicle crash (MVC) fatalities among different race/ethnic groups in urban and rural Arizona.

Method:Using the Fatality Analysis Reporting System and the National Center for Health Statistics Multiple Cause of Death file, MVC fatalities in Arizona from 1990–96 inclusive were classified by gender, race/ethnicity, and urban or rural residence. Age adjusted rates of total, occupant, pedestrian, and alcohol related fatalities were calculated. The total MVC fatality rate for each race/ethnic group was then adjusted for proportion of rural residence.

Results:Compared with non-Hispanic whites (NHWs), American Indians had raised relative risks for MVC fatality in all gender and residence subgroups. Hispanic females and rural Hispanic males had lower relative risks, as did rural African-American men.

Raised relative risks for American Indian men and women included all subgroups: total, occupant, pedestrian, and alcohol related. Hispanic and African-American men both had raised relative risks of pedestrian related fatalities, and Hispanic men had a slightly higher relative risk while Hispanic women had a lower relative risks, for alcohol related fatality. Hispanic men and women and African-American men had lower occupant fatality rates. Close to half (45%) of the excess MVC fatality among American Indians can be attributed to residence in rural areas, where MVC fatality rates are higher. There were 1.85 occupants in crashes involving NHW deaths compared with 2.51 for Hispanics and 2.71 for American Indians (p<0.001). The proportion of occupants not using a seatbelt was higher in Hispanics and American Indians in both urban and rural areas.

Conclusion:The major disparity in MVC fatality in Arizona is among American Indians. The higher MVC fatality rates among American Indians occur in all age groups, in both urban and rural areas, and among occupants and pedestrians. Rural residence, lower rates of seatbelt use, higher rates of alcohol related crashes, a greater number of occupants, and higher rates of pedestrian deaths all contribute to the American Indian MVC fatality disparity.

High rates of pedestrian fatality occur in men in all three race/ethnic minorities in Arizona and among American Indian women. In contrast to other studies, African-Americans and Hispanics did not have raised total MVC fatality rates and compared to NHWs actually had lower rates in the rural areas of the state.
Effect of Italy’s motorcycle helmet law on traumatic brain injuries
Authors: Servadei F , Begliomini C , Gardini E , Giustini M , Taggi F , Kraus J
Published: September 2003

Objectives:To evaluate the impact of a revised Italian motorcycle-moped-scooter helmet law on crash brain injuries.

Design:A pre-post law evaluation of helmet use and traumatic brain injury (TBI) occurrence from 1999 to 2001.

Setting:Romagna region, northeastern Italy, with a 2000 resident population of 983 534 persons.

Participants:Motorcycle-moped rider survey for helmet use compliance and all residents in the region admitted to the Division of Neurosurgery of the Maurizio Bufalini Hospital in Cesena, Italy for TBI.

Outcome measures:Helmet use compliance and change in TBI admissions and type(s) of brain lesions.

Results:Helmet use increased from an average of less than 20% to over 96%. A comparison of TBI incidence in the Romagna region shows that there was no significant variation before and after introduction of the revised helmet law, except for TBI admissions for motorcycle-moped crashes where a 66% decrease was observed. In the same area TBI admissions by age group showed that motorcycle mopeds riders aged 14–60 years sustained significantly fewer TBIs. The rate of TBI admissions to neurosurgery decreased by over 31% and epidural hematomas almost completely disappeared in crash injured moped riders.

Conclusions:The revised Italian mandatory helmet law, with police enforcement, is an effective measure for TBI prevention at all ages.
Home delivery of an injury prevention kit for children in four French cities: a controlled randomized trial
Authors: Sznajder M , Leduc S , Janvrin M P , Bonnin M H , Aegerter P , Baudier F , Chevallier B
Published: September 2003

Objectives:Home delivery of counselling and safety devices to prevent child injuries could help parents to adopt safe behaviour. The aim of this study was to test a safety kit designed and used in Quebec (Canada).

Design and subjects:One hundred families from four towns in the Paris suburbs were visited at home by nurses or doctors when their child reached 6–9 months. Selection criteria were: primipara, medical problem, psychological, and/or socioeconomic difficulties.

Interventions:During the first visit, 50 families (group 1) received counselling and a kit including preventive devices and pamphlets about indoor injuries and ways to avoid them. The other 50 families (group 2) received counselling but not the kit. A second home visit was made 6–8 weeks later.

Main outcome measures:The number of safety improvements was calculated 6–8 weeks after a first home visit. Perceived usefulness of the kit was collected from families and from interviewers.

Results:Between the first and the second visits, safety improvement was significantly higher in the group with the kit. This was mainly related to the risk of fall (p<0.02), fire and burns (p<0.001), poisoning (p<0.01), and suffocation (p<0.001). For improvement related to devices provided in the kit, the difference between the groups was significant: 64.4% improvement in group 1 versus 41.2% in group 2 (p<0.01). The relative risk (RR) of safety improvement between groups was 1.56 (95% confidence interval (CI) 1.35 to 1.80). Even for improvements not related to the kit the difference remained significant: 31.2% in group 1 versus 20.2% in group 2 (p<0.05); RR = 1.54 (95% CI 1.22 to 1.93).

Conclusion:Routine home visits by social services offer a good opportunity to tackle child injury prevention. Free delivery of prevention kits and counselling allow families to modify their behaviour and homes so as to reduce risks.
Trends in serious head injuries among English cyclists and pedestrians: Figure 1
Authors: Cook A , Sheikh A
Published: September 2003

In England the use of bicycle helmets remains low as debate continues about their effectiveness. Time trend studies have previously shown an inverse association between helmet wearing rates and hospital admissions for head injury, but data on helmet wearing are often sparse and admission rates vary for numerous reasons. For the period of this study comprehensive data on helmet wearing are available, and pedestrians are used as a control to monitor trends in admission. Among cyclists admitted to hospital, the percentage with head injury reduced from 27.9% (n = 3070) to 20.4% (n = 2154), as helmet wearing rose from 16.0% to 21.8%. Pedestrian head injury admissions also declined but by a significantly smaller amount. The wearing of a cycle helmet is estimated to prevent 60% of head injuries.
Lessons for increasing awareness and use of booster seats in a Latino community
Authors: Lee J W , Fitzgerald K , Ebel B E
Published: September 2003

Objectives:Latino children are more likely to be unrestrained passengers in motor vehicles than non-Latino children, but little is known about the use of booster seats in Latino families. This study investigates Latino parents’ knowledge, attitudes and beliefs about booster seats, barriers to booster seat use, and effective strategies for message delivery in the Latino community.

Methods:Two focus groups were conducted with Spanish speaking parents. Information was obtained through a written survey and moderated discussions.

Results:Parents were widely misinformed about recommended guidelines for booster seat use, and the majority of participants did not own a booster seat. Parents identified a lack of information, the cost of booster seats, resistance to use by the child or the father, limited space in the vehicle, and unavailability of shoulder belts as barriers to booster seat use. Participants felt that learning more about the new Washington state booster seat law and its consequences would increase booster seat use. Public health messages felt to be effective were those in Spanish, delivered by credible spokespeople such as physicians and teachers, and utilizing the Spanish media.

Conclusions:Campaigns to promote booster seats in the Latino community should be culturally specific, and clear guidelines for booster seat use should be given in Spanish. Legislation may be an important incentive for using booster seats, though reducing their cost and providing strategies to address child resistance and physical constraints of some vehicles are also important.
Immediate care of school sport injury
Authors: Abernethy L , MacAuley D , McNally O , McCann S
Published: September 2003

School sport is a major cause of injury in the post-primary age group. The importance of primary prevention in sport has been identified; however secondary prevention of school related sport injury has not been described in Ireland.

A random sample of 450 schools in Northern Ireland and the Republic of Ireland was studied using a postal questionnaire. Current management of sport injury, with particular interest in the expertise and training of teachers and coaches, was explored.

Replies were received from 333 (74%) schools. There was no physical education teacher with up to date first aid training in 37% schools. Immediate care in terms of mechanisms and equipment to deal with injury was available in 35%–81% of schools responding. Correct response ranged from 65%–90% to four scenarios: commonly presenting yet potentially serious management problems. This study demonstrated deficiencies in sport injury care. In addition to concern about current training, a need for basic life support training is highlighted. These findings have implications for the prevention of school sports injuries.
Design and implementation of injury prevention curricula for elementary schools: lessons learned
Authors: Azeredo R , Stephens-Stidham S
Published: September 2003

Objectives:Project objectives were to: (1) design and produce an easy-to-use, replicable comprehensive injury prevention curriculum for elementary schools; (2) pilot the program to determine instructors’ ease in teaching the material and its usefulness in enhancing student knowledge and behavior change; (3) present material in subject-integrated, grade-specific lessons that would meet state and national student learning objectives; and (4) submit and obtain adoption of the curriculum by the State Department of Education.

Methods:A pilot program was developed, implemented, and evaluated in six intervention and six control schools. The curriculum was revised and implemented in five other schools and finalized according to evaluation results and teachers’ and parents’ suggestions. Community resources such as police, fire, and county health departments participated in program implementation.

Results:The program showed a significant increase from 21% to 36% in seatbelt use during the school year in program schools compared with a 1% decrease in control schools. Bicycle helmet use increased from 0% to 10% in the program schools. Pre-test and post-test results showed significant differences in student knowledge, attitudes, and behaviors within the program schools, and in comparing the program and control schools. On a Likert scale of 1 (poor) to 7 (excellent), teachers rated lesson content, exercises, and the usefulness of materials and resources as 5.8, 5.5, and 5.4, respectively. Evaluations for the revised curricula ranged from 5.7 to 6.2.

Conclusions:The favorable evaluation results resulted in the adoption of the curriculum as a state textbook, and widespread teaching of the curriculum. The product is appropriate and efficacious in these elementary schools and their communities.
Ultrastructural studies onCymbomonas tetramitiformis(Prasinophyceae). I. General structure, scale microstructure, and ontogeny
Authors: Moestrup Øjvind , Inouye Isao , Hori Terumitsu
Published: September 2003

The marine prasinophycean flagellate Cymbomonas tetramitiformis has been established in culture from Japan and Australia and is examined in detail by electron microscopy. The results are described as a series of reports, the first of which deals with the general cell structure and the structure and morphogenesis of the organic scales that cover the surface of the cell and the flagella. The cell produces seven types of organic scales, all of which are manufactured in the cisternae of the Golgi apparatus. Two scale types are deposited on the cell body and cover the cell in three close-fitting layers, two types are confined to the flagellar pit region, and three types cover the flagellar surfaces. Cymbomonas is quadriflagellate and closely related to another quadriflagellate, Pyramimonas, in scale structure and scale ontogeny. It differs markedly in cell symmetry, swimming behavior, and in details of the flagellar apparatus. The flagellar end of the cell with the flagellar pit is surrounded by a horseshoe-shaped rim, which is very different from the usually four-lobed anterior end of Pyramimonas. Cymbomonas also shows resemblance in scale structure to members of the order Mamiellales, notably Mamiella, and to the phycoma-producing genera Pterosperma and Halosphaera. The Japanese isolate of Cymbomonas formed cysts for a short period, and the cyst appears to be homologous with the so-called phycoma stage of Pterosperma and Halosphaera. Since two chloroplasts were seen in the cysts, the cysts probably arise as a result of sexual reproduction. Concomitant with the presence of cysts in the culture, tiny uniflagellate cells were also present, and they probably represent gametes. Cymbomonas was described from the Adriatic in 1913 and was not reported again anywhere until 1986 and 1987 when Throndsen refound it in the Gulf of Naples in southern Italy. It has subsequently been found in large parts of the world and is now readily recognized by its characteristic scales and mode of swimming. It is often common but does not appear to form blooms.Key words: Prasinophyceae, marine nanoplankton, ultrastructure, Cymbomonas.
Morphology and fractal dimension of root systems of maize hybrids bearing the leafy trait
Authors: Costa Carlos , Dwyer Lianne M , Dutilleul Pierre , Foroutan-pour Kayhan , Liu Aiguo , Hamel Chantal , Smith Donald L
Published: September 2003

A rapid and accurate assessment of root morphological characteristics can be important for identifying promising plant genotypes. Scanner-based image analysis has made the measurement of root morphology faster, more accurate, and less subjective, and allows for estimation of fractal dimension (FD). We used scanner-based image analysis to investigate root morphology in leafy vs. conventional maize (Zea mays) genotypes. Two experiments were conducted following a completely randomized design with ten and five replicates. In the first experiment, treatments were factorial combinations of four hybrids (leafy reduced-stature (LRS), non leafy-reduced stature (NLRS), leafy normal stature (LNS), and non leafy normal stature (conventional commercial) hybrid, Pioneer 3979 (P3979)), and four sampling dates (5, 10, 15, and 20 days from transfer to growth pouches). In the second experiment, plants were grown for 15 days from emergence in 10-L plastic pots. This experiment included three maize genotypes (LRS, LNS, and Pioneer 3905 (P3905)). The FD of young root systems was similar for leafy genotypes (FD [Formula: see text] 1.66) and was higher for P3905 (FD [Formula: see text] 1.74). The FD correlated with root characteristics generally included in root growth models (0.68 [Formula: see text] r [Formula: see text] 0.87). Thus, FD could be used to summarize a number of root morphology variables.Key words: root morphology, fractal dimension, root branching, image analysis, maize.
Cadmium accumulation by durum wheat roots in ligand-buffered hydroponic culture: uptake of Cdligand complexes or enhanced diffusion?
Authors: Berkelaar E J , Hale B A
Published: September 2003

The objectives of this study were to test the free ion model of Cd phytoavailability in solutions where the dissolved free ion was buffered by SO4 or EDTA and to examine if Cd2+ diffusion to roots might be limiting to its accumulation in roots. At similar Cd2+ activities, solutions that contained EDTA or a higher nominal SO4 concentration (with SO4 supplied as K2SO4, and more total Cd) resulted in greater accumulation of Cd by roots than predicted by the Cd2+ activity. These solutions were predicted using MINEQL+ (chemical speciation software) to contain greater concentrations of Cd complexes (CdEDTA2 or CdSO04 (aq)) in solution; when SO4 was supplied by MgSO4, the increase in Mg2+ suppressed enhanced accumulation of Cd. Estimates of diffusion of Cd to the roots through the boundary layer and flux of Cd across the root surface, for this study, were similar in magnitude across the range of solution Cd concentrations studied, particularly when Cd uptake was assumed to occur at the root tips only. We conclude that CdEDTA2 and CdSO04 (aq) could have alleviated this diffusion limitation by buffering Cd2+ at the root surface and (or) been taken up directly as a complex.Key words: bioavailability, cadmium, EDTA, SO4, durum wheat, speciation.
Effects of dry heat on the germinability and viability of Scotch thistle (Onopordum acanthium) cypselas: interpopulation and interposition variation
Authors: Qaderi Mirwais M , Cavers Paul B
Published: September 2003

Cypselas (fruits) of four local populations of Scotch thistle, Onopordum acanthium L., were stored for 3 months, heated gradually from room temperature to 50, 75, or 100°C and then gradually cooled to determine effects on germination. Populations responded similarly to this treatment. The lowest germination percentages and slowest rates followed the 100°C treatment, while the fastest germination rates followed 75°C. In a direct-heating experiment, cypselas (from central and peripheral positions in the capitulum) of one population were stored for 41/2 months and then exposed directly to 50, 75, or 100°C for 0.5, 1, or 2 min. This treatment at 75 and 100°C increased germination percentages, with higher percentages for the central cypselas. The 2 min treatment at 100°C yielded the highest percentage and fastest germination rate. Central cypselas were heavier but were similar to peripheral ones in imbibition and in the ratio between cypsela coat and embryo weights. In subsidiary experiments, wax-removed cypselas had smoother surfaces, heated cypselas had visible surface cracks, and germinated cypselas had thinner pericarps. Increases in the percentage and rate of germination in response to dry heat suggest that seedlings of O. acanthium may emerge sooner and in greater numbers following a fire event on disturbed or agricultural lands.Key words: cypsela, dry heat, germination, Onopordum acanthium, Scotch thistle, viability.
A comparative epidermis study of the Athabasca sand dune willows (Salix; Salicaceae) and their putative progenitors
Authors: Cooper Ranessa L , Cass David D
Published: September 2003

The Athabasca sand dunes are located on the south shore of Lake Athabasca in northern Alberta and Saskatchewan, Canada. Four willow shrubs (Salix; Salicaceae) occur on the open sands, two of which are endemic to the Athabasca sand dunes. Light and scanning electron microscopy were used to quantify stomatal frequency, stomatal index, trichome density, and cuticle thickness, for the Athabasca sand dune willows and their associated putative progenitors. The Athabasca sand dune taxa (Salix brachycarpa var. psammophila, Salix planifolia subsp. tyrrellii, Salix silicicola, and Salix turnorii) occur primarily on the inner dunes, and each has certain leaf epidermal features that appear to be adaptive to the exposed nature of the open sand habitat and the high light intensity. Salix brachycarpa var. psammophila and S. silicicola have tomentose leaves, with trichome densities that are significantly greater than those of their respective widespread progenitors. Salix planifolia subsp. tyrrellii and S. turnorii have amphistomatic leaves and substantially thicker cuticles than their associated progenitors. This investigation is the first to compare adaptive leaf epidermis features within the derivativeprogenitor Salix pairs. Considerations for the significance of amphistomaty in the Athabasca sand dune Salix taxa are discussed.Key words: Athabasca sand dunes, cuticle, Salix, stomata, trichomes, willow.
Mass loss and nitrogen dynamics during the decomposition of a 15N-labeled N2-fixing epiphytic lichen, Lobaria oregana
Authors: Holub Scott M , Lajtha Kate
Published: September 2003

We studied mass loss and nitrogen dynamics during fall and spring initiated decomposition of an N2-fixing epiphytic lichen, Lobaria oregana (Tuck.) Müll. Arg., using 15N. We developed a method of labeling lichens with 15N for use in a decomposition study that involved spraying lichen material with a nutrient solution containing 15N-enriched ammonium. Through the first 180 days of sampling, lichens placed in the field during the spring had a smaller decay constant (k = 1.24 year1) than the lichens placed in the field during the fall (k = 3.1 year1). However, both spring and fall lichen samples were decomposed beyond recognition after 1 year. Patterns in exogenous N uptake and N concentration did not differ by season. Both spring and fall lichens took up N from the surrounding environment during decay while simultaneously losing N to the environment. The N concentration in both sets of lichen additions increased during decay to a peak of around 2.8% N, equal to a C to N ratio of about 16, and then began to decrease. This indicates that early in decay, net N immobilization occurred in the remaining lichen, but this was followed by net N mineralization in later stages of decay.Key words: decomposition, nitrogen, Lobaria oregana, lichen, mineralization, immobilization.
Infundibulomyces: a new genus of coelomycetes from Thailand
Authors: Plaingam Narumol , Somrithipol Sayanh , Jones E B. Gareth
Published: September 2003

The genus Infundibulomyces is proposed for coelomycetous fungi with nidulariaceous-like conidiomata and bipolar appendaged conidia. Infundibulomyces cupulata sp. nov., collected from fallen leaves of Lagerstroemia sp. from Thailand, is described as the type species of the genus. This fungus is illustrated at the light microscope and scanning electron microscope level and compared with other morphologically related taxa. Cupulate conidiomata are uncommon and Infundibulomyces is compared with these.Key words: anamorphic fungi, coelomycete, Infundibulomyces, Thailand, tropical.
Novel variation in the floral development of two species ofParthenocissus
Authors: Wilson Trevor , Posluszny Usher
Published: September 2003

This study compares the development of the inflorescences and flowers of Parthenocissus quinquefolia (Virginia creeper) and Parthenocissus tricuspidata (Boston ivy). The development of the reproductive shoots is described from inception to maturity using epi-illumination and scanning electron microscopy. In both species, the shoot apex initiates inflorescence primordia low on the apical flank. An inflorescence primordium produces several bract-opposed branches, which in early development resembles the main shoot. As inflorescence development continues, branch primordia initiate as increasingly larger portions than the inflorescence apical meristem. By late development, branch primordia initiate as larger portions than the apex, which is a process that has been observed in other vitaceous inflorescences. With respect to initiation and early development, the Parthenocissus inflorescence is very similar to the tendril, which has been previously studied; these two organs have never been described to be so similar, and their likeness to the shoot, in early development, provides an idea as to how they may have arisen. An inflorescence branch terminates as a dichasium, which is formed by two nearly simultaneous branching events. Parthenocissus tricuspidata flowers develop a more robust gynoecial disc and stigma than in the P. quinquefolia flower; but the calyx is ring-like in the former and cup-like in the latter. Contrary to the previous assumption that there are no differences in reproductive biology within genera of the Vitaceae, this study has clearly demonstrated variation between two species of Parthenocissus.Key words: floral, development, monopodial, Parthenocissus, inflorescence, Vitaceae.
Lithospheric roots beneath western Laurentia: the geochemical signal in mantle garnets
Authors: Canil D , Schulze D J , Hall D , Hearn Jr. B C , Milliken S M
Published: September 2003

This study presents major and trace element data for 243 mantle garnet xenocrysts from six kimberlites in parts of western North America. The geochemical data for the garnet xenocrysts are used to infer the composition, thickness, and tectonothermal affinity of the mantle lithosphere beneath western Laurentia at the time of kimberlite eruption. The garnets record temperatures between 800 and 1450°C using Ni-in-garnet thermometry and represent mainly lherzolitic mantle lithosphere sampled over an interval from about 110260 km depth. Garnets with sinuous rare-earth element patterns, high Sr, and high Sc/V occur mainly at shallow depths and occur almost exclusively in kimberlites interpreted to have sampled Archean mantle lithosphere beneath the Wyoming Province in Laurentia, and are notably absent in garnets from kimberlites erupting through the Proterozoic Yavapai Mazatzal and Trans-Hudson provinces. The similarities in depths of equilibration, but differing geochemical patterns in garnets from the Cross kimberlite (southeastern British Columbia) compared to kimberlites in the Wyoming Province argue for post-Archean replacement and (or) modification of mantle beneath the Archean Hearne Province. Convective removal of mantle lithosphere beneath the Archean Hearne Province in a "tectonic vise" during the Proterozoic terminal collisions that formed Laurentia either did not occur, or was followed by replacement of thick mantle lithosphere that was sampled by kimberlite in the Triassic, and is still observed there seismically today.
A new late-glacial sea-level record for St. George's Bay, Newfoundland
Authors: Bell Trevor , Batterson Martin J , Liverman David GE , Shaw John
Published: September 2003

A new relative sea-level curve is presented for St. George's Bay, southwest Newfoundland, based on (i) a revised stratigraphic framework and depositional model for glacial and marine deposits exposed in coastal sections and (ii) 19 new radiocarbon dates on shells from emerged and submerged marine deposits, including fossiliferous diamictons. The data produce a type B sea-level curve, falling steeply from an extrapolated marine limit of 105 m above sea level at 14.0 14C ka BP, passing below modern sea level at ~10.6 14C ka BP, to a lowstand of 25 m at ~9.4 14C ka BP, and rising again close to modern sea level by 5.0 14C ka BP. Marine limits in the northern part of the bay have lower elevations (2765 m) due to delayed ice retreat of up to 1.2 ka. Between 12.8 and at least 12.3 14C ka BP, glaciofluvial outwash graded to falling sea levels between 27 and 17 m above present throughout the bay, whereas lowstand deltas were constructed in sheltered locations at the outlets of major river systems, when sea level was 25 m below present. Establishment of the sea-level lowstand at ~9.4 14C ka BP is supported by new seismic data and radiocarbon dates from St. George's Bay and also from White Bear Bay on the south coast of Newfoundland. Short-term fluctuations in emergence rates of 12 m/century between 12.5 and 9.5 14C ka BP are attributed to variable eustatic sea-level rise, superimposed on a declining local glacio-isostatic adjustment.