bluuebunny/crossref_metadata_2025_split huggingface dataset:
The natural history of periodontal disease in man
Authors: Löe Harald , ÅNerud ÅGe , Boysen Hans , Smith Martyn 
Published: July 2006

This is the first in a series of reports on a longitudinal investigation of the initiation and progress of periodontal disease in man. One group was established in Norway in 1969 and consisted of 565 male students and teachers between 17 and 30+years. A second group of comparable age was established in Sri Lanka in 1970 and consisted of 480 tea laborers. Both groups were scored for various disease parameters at start and at intervals during the subsequent seven years. This paper describes the design of the investigation and periodontal state of the two groups at baseline.The results show that th Norwegian group had good to excellent oral hygiene and mild gingivitis. Supra‐and subgingival calculus were inconspicous and untreated slowly with age. The mean loss of attachment in the 30+year old was less than one millimeter.Tht Sri Lankan tea laborers showed poor oral hygiene, abundance of calculus and generalized moderate to severe gingivitis. Caries and dental restorations were non‐existent. Slight loss of attachment was seen in the 15year old and increased through the twenties. The 30+years old Sri Lankan tea laborer showed a mean loss of more than 3 mm and a subsantial number of teeth exhibited attachment loss in excess of 10 mm.The baseline analysis indicated that due to the choice of study groups and design, the longitudenal data will lend themselves to describing the initiation, pattern of development and the rate of progress of periodontal disease during major portions of the abult life of these people.
Periodontal disease associated with Shigella flexneri in rhesus monkeys
Authors: Armitage G. C. , Newbrun E. , Hoover C. I. , Anderson J. H. 
Published: July 2006

The clinical, microbiologic, and histopathologic features of Shigella flexneri‐associated periodontal disease of rhesus monkeys were examined. Eighteen subgingival plaque samples and 17 gingival biopsy specimens were taken from 8 rhesus monkeys harboring S. flexneri orally. All plaque samples and three of the biopsy specimens were processed aerobically and anaerobically on selective and nonselective media. The remaining biopsy specimens were prepared for light or electron microscopic observation. An additional 11 subgingival plaque samples from 6 monkeys not suspected of orally harboring S. flexneri were also processed microbiologically.In the monkeys harboring Shigella orally, S. flexneri serotype 4 was isolated from 16 of the 18 subgingival plaque samples. It constituted a minor plaque component in all 16 positive sites, usually less than 0.1 % of the recoverable flora. S. flexneri was not detected in any of the subgingival plaques from control monkeys. Gingival sites harboring S. flexneri were characterized by extremely intense clinical inflammation. Histopathologic observations included ulceration of the pocket wall and heavy lymphocytic and plasma cell infiltration of the connective tissue. At the ultrastructural level, unidentified bacteria were occasionally observed between, and possibly within, intact epithelial cells adjacent to areas of ulceration.The results suggest that S. flexneri, though a numerically minor component of the plaque flora, may be important in the pathogenesis of the periodontal disease observed in this study.
In vitro breakdown of gingival tissue by elastase from human polymorphonuclear leukocytes An electron microscopic study
Authors: Cergneux M. , Andersen E. , Cimasoni G. 
Published: July 2006

Several biopsies of human marginal gingiva were collected from clinically healthy and from slightly inflamed sites. The biopsies from one given site were divided and treated as follows: one portion was immediately fixed and used as a reference; the others were incubated for two hours either in culture medium alone, or in the same medium with different concentrations of elastase purified from human polymorphonuclear leukocytes. The biopsies were then fixed and examined by electron microscopy. It was found that elastase caused an enlargement of the intercellular spaces of the oral gingival epithelium, interruptions of the basement lamina, and loss of collagen in the underlying connective tissue.Biopsies collected from severely inflamed sites were also studied in the electron microscope. Some of the ultrastructural alterations observed in these inflamed tissues were similar to those experimentally induced by elastase.
Biology of suckers: late‐formed shoots in sugarcane
Authors: BONNETT G D , SALTER B , ALBERTSON P L 
Published: July 2006

SummarySuckers in sugarcane are tillers that form late in the growing season after the population of main stalks has been established. Their biology has rarely been studied, though unsubstantiated comments relating to their morphology, development and number are abundant. In this paper, the literature is reviewed and new experiments presented. Comparison of suckers, emerging plant and ratoon cane showed that suckers have a different leaf and stem morphology. Suckers have a greater diameter at their stem base and shorter and wider leaves than primary stalks of a similar age. In 1 ‐year‐old crops, suckers have been demonstrated to decrease the net sucrose concentration of harvested material by diluting sucrose in the main stalks. By comparing main stalks without suckers to those that have initiated suckers, evidence is presented that suckers may also be decreasing the sucrose content of the stalks from which they are growing. Genotypic and environmental factors influence sucker number. Several experiments were designed to identify environmental stimuli for suckering. Increased nitrogen, through application late in the growing season, was found to increase the numbers of suckers present. Manipulation of the light environment of main stalks showed that a change in light quality (but not necessarily quantity) stimulated suckering. Further work is underway to define how these environmental stimuli lead to sucker initiation and growth. Major scientific questions that should be addressed are: the identification of other potential environmental stimuli, how the signals are perceived and translated into sucker initiation, and why suckers have different morphology. The practical challenge is to combine the new information about sucker biology and develop from it strategies to alter agronomy and select new cultivars that results in decreased suckering.
A comparison of the carbohydrate composition and kinetic properties of sucrose phosphate synthase (SPS) in transgenic tobacco (Nicotiana tabacum) leaves expressing maize SPS protein with untransformed controls
Authors: BAXTER CHARLES J , FOYER CHRISTINE H , ROLFE STEPHEN A , QUICK W PAUL 
Published: July 2006

SummaryTobacco plants, transformed with a maize sucrose phosphate synthase (SPS) cDNA clone, had threefold increased SPS activity compared to wild‐type tobacco. Measurement of SPS maximal activity and protein abundance using specific antibodies to the maize protein showed that the specific activity of the maize SPS protein was maintained when expressed in tobacco. Comparison of the kinetic properties of SPS in the transgenic lines compared to either wild‐type maize or tobacco revealed that the heterologously expressed protein had reduced affinity for both substrates (fructose‐6‐phosphate and UDP‐glucose) and reduced sensitivity to allosteric inhibition by inorganic phosphate. Moreover, the extent of light‐induced activation was reduced in the transgenic lines, with smaller changes observed in the Km for both F6P compared to maize and tobacco wild‐type plants. Increased sucrose concentrations were observed in the transgenic lines at the end of the photoperiod and this was linearly related to SPS activity and associated with a parallel decrease in starch content. This suggests that SPS is a major control point for carbohydrate partitioning between starch and sucrose during photosynthesis.
Environmental effects on dry matter partitioning between shoot and root of crop plants: relations with growth and shoot protein concentration
Authors: ANDREWS M , RAVEN J A , SPRENT J I 
Published: July 2006

SummaryThe literature on environmental effects on dry matter partitioning in higher plants, in particular crop plants, is reviewed focussing on changes in shoot to root dry weight ratio (S:R). Of particular consistency is the finding that S:R increases with increased nitrogen (N) supply. Relations between nitrogen (N) supply, growth, S:R and tissue N and protein concentration are examined. In some cases, the increase in S:R with increased N supply is likely to have been at least in part an effect on growth and development, but there is unequivocal evidence that N affects S:R independently of growth and development. A positive correlation between S:R and leaf protein concentration is highlighted. It is argued that the N effect on S:R outside the effect on growth and development is related to increased shoot protein concentration. Specifically, shoot and root growth are colimited by local carbon (C) and N (primarily protein) substrate concentrations and shoot growth will increase relative to root growth with increased N substrate availability due to the proximity of the shoot to the C source. It is further argued that results in the literature are consistent with the proposal that macronutrient, water, irradiance, CO2 and temperature effects on S:R are often primarily mediated through their effects on growth and development, and shoot protein concentration and hence shoot growth.
The challenge of remobilisation in plant nitrogen economy. A survey of physio‐agronomic and molecular approaches
Authors: MASCLAUX CÉLINE , QUILLERÉ ISABELLE , GALLAIS ANDRÉ , HIREL BERTRAND 
Published: July 2006

SummaryIn this article, we discuss the ways in which our understanding of the controls of nitrogen remobilisation in model species and crop plants have been increased through classical physiological studies and the use of transgenic plants or mutants with modified capacities for nitrogen or carbon assimilation and recycling. An improved understanding of the transition between nitrogen assimilation and nitrogen recycling will be vital, if improvements in crop nitrogen use efficiency are to reduce the need for excessive input of fertilisers and improve or stabilise yield. In this review, we present an overall view of past work and more recent studies on this topic, using different plants systems and models depicting the biochemical and molecular events occurring during the transition between sink leaves and source leaves. These models may provide a way to identify the nature of the metabolic or developmental signals triggering in a coordinate manner nitrogen and carbon recycling during leaf senescence.Another way of developing crop varieties with improved nitrogen use efficiency, and identifying key elements controlling the process of nitrogen remobilisation, is the use of quantitative genetics. We present and discuss recent findings on the genetic variability and basis of nitrogen use efficiency in crops in general and in maize in particular. A genetic approach using maize recombinant inbred lines was undertaken allowing the detection of Quantitative Trait Loci (QTLs) for morphological traits, grain yield and its components under high nitrogen or low nitrogen input. Co‐mapping was observed between genes encoding enzymes involved in nitrogen assimilation (nitrate reductase, glutamine synthetase) and these Quantitative Trait Loci. All coincidences were consistent with the expected physiological function of the corresponding enzyme activities. This work strongly suggests that in maize, nitrogen use efficiency can be improved both by marker‐assisted selection and genetic engineering.
Stay‐green: A consequence of the balance between supply and demand for nitrogen during grain filling?
Authors: BORRELL ANDREW , HAMMER GRAEME , VAN OOSTEROM ERIK 
Published: July 2006

SummaryRetention of green leaf area in grain sorghum under post‐anthesis drought, known as stay‐green, is associated with greater biomass production, lodging resistance and yield. The stay‐green phenomenon can be examined at a cell, leaf, or whole plant level. At a cell level, the retention of chloroplast proteins such as LHCP2, OEC33 and Rubisco until late in senescence has been reported in sorghum containing the KS19 source of stay‐green, indicating that photosynthesis may be maintained for longer during senescence in these genotypes. At a leaf level, longevity of photosynthetic apparatus is intimately related to nitrogen (N) status. At a whole plant level, stay‐green can be viewed as a consequence of the balance between N demand by the grain and N supply during grain filling. To examine some of these concepts, nine hybrids varying in the B35 and KS19 sources of stay‐green were grown under a post‐anthesis water deficit. Genotypic variation in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen (SLN) and N uptake during grain filling. Matching N supply from age‐related senescence and N uptake during grain filling with grain N demand found that the shortfall in N supply for grain filling was greater in the senescent than stay‐green hybrids, resulting in more accelerated leaf senescence in the former. We hypothesise that increased N uptake by stay‐green hybrids is a result of greater biomass accumulation during grain filling in response to increased sink demand (higher grain numbers) which, in turn, is the result of increased radiation use efficiency and transpiration efficiency due to higher SLN. Delayed leaf senescence resulting from higher SLN should, in turn, allow more carbon and nitrogen to be allocated to the roots of stay‐green hybrids during grain filling, thereby maintaining a greater capacity to extract N from the soil compared with senescent hybrids.
Identification of mutants in phosphorus metabolism
Authors: LLOYD JULIE C , ZAKHLENIUK OKSANA V , RAINES CHRISTINE A 
Published: July 2006

SummaryPhosphorus availability is often limiting for plant growth. However, little is known of the pathways and mechanisms that regulate phosphorus (P) uptake and distribution in plants. We have developed a screen based on the induction of secreted root acid phosphatase activity by low‐P stress to identify mutants of Arabidopsis thaliana with defects in P metabolism. Acid phosphatase activity was detected visually in the roots of A. thaliana seedlings grown in vitro on low‐P medium, using the chromogenic substrate, 5‐bromo‐4‐chloro‐3‐indolyl‐phosphate (BCIP). In low‐P stress conditions the roots of wild‐type plants stained blue, as the induced root acid phosphatase cleaved BCIP to release the coloured product. Potential mutants were identified as having white, or pale blue, roots under these conditions. Out of approximately 79 000 T‐DNA mutagenised seedlings screened, two mutants with reduced acid phosphatase staining were further characterised. Both exhibited reduced growth and differences in their P contents when compared to wild‐type A. thaliana. The mutant with the most severe phenotype, pho3, accumulated high levels of anthocyanins and starch in a distinctive visual pattern within the leaves. The phenotypes of these mutants are distinct from two previously identified phosphorus mutants (phol and pho2) and from an acid phosphatase deficient mutant (pupl) of A. thaliana. This suggested that the screening method was robust and might lead to the identification of further mutants with the potential for increasing our understanding of P nutrition.
The impact of irrigation frequency on population density of thrips, Thrips tabaci Rom (Thripidae, Thysanoptera) and yield of onion in E1 Rahad, Sudan
Authors: KANNAN H O , MOHAMED M B 
Published: July 2006

SummaryVegetable farmers of the El Rahad Scheme (a newly developed scheme situated between latitude 13°31′–14°25′ north and longitude 33°31–34°32′ east) used to extend irrigation frequency for onion production as they believed it would hamper and suppress thrips incidence. Thrips, T. tabaci, is the only major insect pest of onion in the El Rahad Scheme and the influence of irrigation intervals on the population density of the pest and on onion yield was not quantified. Irrigation is a factor in the development of crop pests and the levels of the pest population are related to the commencement of irrigation. The effect of irrigation frequency on the development of onion thrips and yield was investigated and the response was found to be a significant increase in the population density of the pests from February to March with shorter irrigation frequency. A steady increase of thrips population was noted from February and March and a sharp decline was recorded in April during both the 1992/93 and 1993/94 seasons. At wider irrigation intervals, levels of the pest population were significantly less from February to March during both seasons. Total bulb yield and average bulb weight were significantly higher at shorter irrigation frequencies when compared with extended frequencies. The same pattern of results existed throughout the course of the experiment.
Progress of cassava mosaic virus disease and whitefly vector populations in single and mixed stands of four cassava varieties grown under epidemic conditions in Uganda
Authors: SSERUBOMBWE W S , THRESH J M , OTIM‐NAPE G W , OSIRU D O S 
Published: July 2006

SummaryProgress curves of cassava mosaic virus disease (CMD) and populations of the whitefly vector (Bemisia tabaci) were assessed using four cassava varieties grown alone and as a random mixture in two experiments established under epidemic conditions at a site near Kampala in southern Uganda. There were significant differences in final CMD incidence and in the areas under the disease progress curves between varieties when grown alone and as a mixture in both experiments. Variety Ebwanateraka had the highest incidence and SS4 the lowest, even though it supported the largest populations of adult whiteflies. The overall incidence of CMD in the mixture was similar to that in pure stands of the partially resistant Nase 2 and greater than in the resistant Migyera and SS4. Compared to pure stands, incidence of CMD in each component of the mixture was reduced significantly only in Ebwanateraka, whereas vector populations were less only in SS4 and Nase 2. On several observation dates the actual incidence of CMD and populations of adult whiteflies in the mixture were significantly less than expected values estimated from the results for the four varieties when each was grown alone. A highly significant positive relationship was established for each variety between peak populations of adult whitefly and leaf area index at the time. The implications of the findings and the scope for future research on the use of varietal mixtures for the management of CMD are discussed.
Probable mechanical transmission of a virus‐like agent from rose rosette disease‐infected multiflora rose to Nicotiana species
Authors: ROHOZINSKI JAN , EPSTEIN A H , HILL J H 
Published: July 2006

SummaryAs part of efforts to identify the causal agent of the rose rosette disease (RRD) of multiflora rose (Rosa multiflora Thunb.), root tip extracts from both symptomatic and nonsymptomatic roses were used to mechanically inoculate leaves of Nicotiana glutinosa. Pale green spots were observed along the margins of the major leaf veins only on leaves inoculated with extracts prepared from symptomatic rose plants. Light microscopy revealed abnormal development of the palisade and spongy mesophyll cells in the symptomatic tissue, although no virus‐like particles (VLPs) were observed by electron microscopy. However, VLPs were observed in cells from tissue adjacent to the leaf veins and bordered by the pale green spots. Inoculation of N. benthamiana with extracts from symptomatic N. glutinosa initially did not result in visible symptoms on N. benthamiana inoculated leaves. However, approximately 4 wk post inoculation, splitting of leaf tissue across and along major leaf veins in expanding leaves occurred. In later stages of leaf expansion some leaves split in regions not associated with veins. Light microscopy of thick sections revealed separation between palisade cells and groups of small dead cells in the mesophyll tissue of expanding systemically infected leaf blades. Electron microscopy revealed crystalline arrays in the cytoplasm of mesophyll cells. No abnormal cellular changes were observed in plants inoculated with extracts prepared from nonsymptomatic rose plants.
Evaluation of some garlic (Allium sativum L.) mutants resistant to white rot disease by RAPD analysis
Authors: NABULSI I , AL‐SAFADI B , ALI N MIR , ARABI M I E 
Published: July 2006

SummaryRandom amplified polymorphic DNA (RAPD) analysis was used to evaluate genetic diversity among eight garlic mutants resistant to white rot disease (Sclerotium cepivorum). Twelve of the 13 synthetic random primers were found to identify polymorphism in amplification products. Mutants characterised with moderate resistance to white rot were closely related to the control using cluster and correlation analyses. On the other hand, highly resistant mutants were quite distant from the control with low correlation coefficients. The banding patterns produced by primer OPB‐15 (GGAGGGTGTT) with highly resistant mutants may by used as genetic markers for early selection of resistant plants.
The influence of genetics on future crop production strategies: from traits to genes, and genes to traits
Authors: SNAPE J 
Published: July 2006

SummaryThis paper discusses how a genetical approach to plant physiology can contribute to research underpinning the production of new crop varieties. It highlights the interactions between genetics and plant breeding and how the current advances in genetics and the new science of genomics can contribute to our understanding of the genetical control of key agronomic traits ‐ the process of ‘translating’ traits to identified and mapped genes. Advances in genomics, such as the sequencing of whole genomes and expressed sequence tags, are producing information on genes and gene structures, but without knowing their function. A great deal more biology will be necessary to translate gene structure to function ‐ the process of translating genes to traits. Combining these ‘forward’ and ‘reverse’ genetic approaches will allow us to get comprehensive knowledge of the biology of agronomic traits at the physiological, biochemical and molecular levels, so that the ‘circuitry’ of our crop plants can be elucidated. This will enable plant breeders to manipulate crop phenotype using marker‐assisted breeding or genetic engineering approaches with a precision not previously possible.