128 research outputs found
Studies on plant gene transfer systems
Full text linkA number of methods for the transfer of genes to plants are assessed in this work. The potential of Agrobacterium tumefaciens infection of germinating pollen tubes in vitro as a method of gene transfer was investigated and evidence presented for an essential pre-requisite of infection, that of attachment of Agrobacteria to the pollen tube wall, with both a dicot and a monocot species. In addition, the possibility of direct uptake of DNA molecules by germinating pollen tubes was suggested by in vitro uptake studies. Microinjection of DNA molecules into the loculus of ovaries, with the aim of facilitating in vivo DNA uptake by the male and/or female gametes, was investigated with Salpiglossis sinuata ovaries. Evidence was presented for the persistence of DNA molecules in the ovary loculus and gene transfer using a non-oncogenic Agrobacterium plasmid vector was attempted and the resulting progeny were screened for transformation: The techniques of Agrobacterium-infection of leaf discs and direct DNA uptake by protoplasts were applied to Nicotiana tabacum. DNA transformation vectors containing a kanamycin resistance marker gene and a chimeric pea seed storage protein gene were constructed for use in this study. The seed-specific promoter of the pea legumin A gene was replaced with the nopaline synthase promoter that is expressed in a more constitutive manner in plant tissues. Kanamycin resistant transgenic plants were regenerated following both transformation techniques and the presence and structure of inserted foreign DNA was determined by Southern blot hybridizations. The transmission of kanamycin resistance to transformant progeny after self-fertilization demonstrated characteristic Mendelian inheritance. The expression of the inserted legumin gene in leaf tissue of a number of Agrobacterium-denved transformants was assessed by Northern blot hybridization; legumin transcripts were detected, although the protein immuno-detection procedures of Western blotting and ELISA did not detect legumin in the seeds or leaf tissue of transgenic plants derived from either transformation technique
Functionalised DNA - introducing and applying a versatile porphyrin molecular ruler
No full textPorphyrin moieties were rigidly attached to DNA to generate an accurate molecular ruler. Molecular ruler analysis was conducted using steady-state fluorescence, circular dichroism and small angle X-ray scattering spectroscopic techniques, in an attempt to analyse the FRET, exciton coupling and scattering intensity between different porphyrin-porphyrin labelled DNA combinations. A 21-mer test sequence was labelled with a porphyrin in one position on one strand, and seven different positions on seven complementary strands, to overall give seven porphyrin-porphyrin inter-strand combinations. Steady-state fluorescence and circular dichroism spectroscopic analysis of the Soret band revealed individual Watson-Crick bases pair molecular ruler sensitivity. Small angle X-ray scattering attempts between metallated-porphyrin entities did not reveal sufficient scattering at low concentrations, in contrast, an iodinated analogue of the porphyrin system did displayed scattering correlating to different iodine iodine distances. After calibration of the porphyrin system, the moieties were applied to study protein-DNA interactions between Tus, a 36 KDa DNA binding protein, and Ter, a specific 21-mer DNA sequence. Molecular ruler nalysis of the complex required an extended version of the Ter DNA sequence to which modifications were attached. Established FRET pairs FAM and TAMRA were applied to investigate protein-DNA complexation. Native PAGE analysis revealed Tus binds to the extended DNA via a sliding mechanism. Fluorescence analysis of the established FRET pairs identified changes in fluorescence not correlating to changes in FRET, and instead was attributed to emission quenching upon protein binding. Applying the zinc and free base porphyrin version displayed subtle changes in the Soret band circular dichrosim upon complexation, indicating small DNA helical change upon complexation. A 45-mer DNA sequence was designed to form multiple hairpin-duplex conformations with the addition of an appropriate complementary strand. Attaching FRET pairs to the extremes of the DNA sequence enabled multiple DNA conformations, and hence FRET distances to be obtained from one doubly modified DNA sequence. The combinations were characterised by UV-Vis, fluorescence and circular dichroism spectroscopy. Finally, terpyridine labelled DNA sequences selectively formed DNA nanotubes through orthogonal hydrogen bonding and metal complexation interactions. Short DNA strands were designed to self-assemble into long duplexes through a sticky-end approach. Addition of weakly binding metals such as zinc induced the formation of tubular arrays consisting of DNA bundles 50-200 nm wide and 2-50 nm high. TEM displayed additional long distance ordering of the terpyridine-DNA complexes into fibers
Sample representation in a psychological treatment study after single event paediatric trauma
Full text linkChildren and their families who attended an emergency department following a single traumatic incident and who agreed to participate in a psychological treatment study (N = 211) were compared with nonparticipants (N = 2333) on several measures of trauma and injury severity: duration of admission and heart rate in the emergency department, emergency transport and admission to hospital, injury severity score, and triage code. Within the nonparticipant population, those who requested further information about the study (N = 573) were exposed to more severe trauma or injury than other nonparticipants (N = 1760). In addition, participants were exposed to more severe trauma or injury than either group of nonparticipants. These observations indicate that those exposed to more severe trauma or injury do not avoid participation in psychological treatment studies. Findings can therefore be generalized to those with more severe exposure, but not to the population as a whole
The impact of the newer knowledge of nutrition: nutrition science and nutrition policy, 1900-1939.
Full text linkIdeas concerning relationships between diet and health in the UK are
traced from the 1904 Comittee on Physical Deterioration to the outbreak
of World War II. Archive material is used to describe the often
conflicting views of the Medical Research Council and the Ministry of
Health and Board of Education concerning the public health applications
of nutrition science. In particular, the work of the Ministry of
Health's first Advisory Comittee on Nutrition, which was appointed in
1931, is reviewed and evaluated. The debate among public healh
practitioners over the nature, cause and extent of the 'nutrition
problem' is documented and the role in this debate of official dietary
guidelines which appeared during the 1930s, is assessed.
The Impact of the Newer Knowledge of Nutrition on welfare feeding policy
Is evaluated in the context of the official promotion of milk feeding in
schools. In particular, Corry Mann's experimental evidence which was
used to endorse this policy, is reconsidered, and it is shown that the
NRC view that the trial was proof of the presence in milk of a "growth
factor" which produced preferential growth efficiency in adequately fed
children , was in error. From a re-evaluation of the evidence it is
suggested that the experiment merely recorded catch-up growth in a group
of poorly nourished children. The view that there existed an extensive
nutritional problem due to poor quality diets is examined and
challenged.
Both dietary survey data and anthropometric evidence are used to present
the case that there was throughout the period studied a widespread
problem of underfeeding among the poor and that intervention strategies
based on the Newer Knowledge were not an appropriate method of dealing
with this problem. This casts doubts on the widely held view that there
was a need for nutrition education and suggests that the problem was one of poverty rather than Ignorance. Disaggregated anthropometric data
located by the author are analysed according to NCHS standards to assess
the prevalence of underfeeding. Significantly higher prevalences of
stunting than low weight-for-age exist in all data sets; this phenomenon
is considered in detail and low weight-for-age is proposed as the
preferred index of malnutrition in 20th Century historical studies.
Attention is drawn to the relevance of these studies for the current
nutrition and public health debate
Population genetic analysis of two species of non-indigenous riparian weeds in northeast England in the context of their spatial ecology
Full text linkThe population genetic structure of two species of invasive non-indigenous riparian weeds in the Northeast of England was investigated using microsatellite markers. Heracleum mantegazzianum and Impatiens glandulifera were introduced into the UK from Asia. The first records of the species in the Tees, Tyne and Wear catchment areas were in 1944 and 1892 respectively. Both species have spread rapidly, and are present over a wide area of the catchments. The pattern of genetic variation was investigated in order to determine the importance of anthropogenic introduction, and life-history and dispersal strategies to the distribution of the species. Twelve populations of each species were sampled from the Tees, Tyne and Wear catchments as well as an independent population for comparison. Genomic libraries were constructed and screened for dinucleotide repeat microsatellite loci. Four polymorphic loci of H. mantegazzianum and three of I. glandulfera were identified, and each species was also screened for variation using one universal chloroplast microsatellite locus. A large amount of variation was found in both species as the loci of H. mantegazzianum had between nine and twenty alleles and those of I. glandulifera between eight and sixteen alleles. Results revealed greater overall variation between populations from different catchments than those in the same catchment. Within a catchment, there was evidence of isolation by distance for both species in one out of two catchments examined. Populations of I. glandulifera showed greater temporal variation and there was more variation both overall and within a catchment in this species. This is likely to be due to the larger number of individuals present, and the wider distribution of this species. Low levels of chloroplast variation were found in both species. This may reflect a lack of variation in the material introduced into the UK
Prochlorococcus and Synechococcus have evolved different adaptive mechanisms to cope with light and UV stress
Full text linkProchlorococcus and Synechococcus, which numerically dominate vast oceanic areas, are the two most abundant oxygenic phototrophs on Earth. Although they require solar energy for photosynthesis, excess light and associated high UV radiations can induce high levels of oxidative stress that may have deleterious effects on their growth and productivity. Here, we compared the photophysiologies of the model strains Prochlorococcus marinus PCC 9511 and Synechococcus sp. WH7803 grown under a bell-shaped light/dark cycle of high visible light supplemented or not with UV. Prochlorococcus exhibited a higher sensitivity to photoinactivation than Synechococcus under both conditions, as shown by a larger drop of photosystem II (PSII) quantum yield at noon and different diel patterns of the D1 protein pool. In the presence of UV, the PSII repair rate was significantly depressed at noon in Prochlorococcus compared to Synechococcus. Additionally, Prochlorococcus was more sensitive than Synechococcus to oxidative stress, as shown by the different degrees of PSII photoinactivation after addition of hydrogen peroxide. A transcriptional analysis also revealed dramatic discrepancies between the two organisms in the diel expression patterns of several genes involved notably in the biosynthesis and/or repair of photosystems, light-harvesting complexes, CO2 fixation as well as protection mechanisms against light, UV and oxidative stress, which likely translate profound differences in their light-controlled regulation. Altogether our results suggest that while Synechococcus has developed efficient ways to cope with light and UV stress, Prochlorococcus cells seemingly survive stressful hours of the day by launching a minimal set of protection mechanisms and by temporarily bringing down several key metabolic processes. This study provides unprecedented insights into understanding the distinct depth distributions and dynamics of these two picocyanobacteria in the field
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