Development of multiple strain competitive index assays for <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> using pIMC; a new site-specific integrative vector

Background  

The foodborne, gram-positive pathogen, Listeria monocytogenes, is capable of causing lethal infections in compromised individuals. In the post genomic era of L. monocytogenes research, techniques are required to identify and validate genes involved in the pathogenicity and environmental biology of the organism. The aim here was to develop a widely applicable method to tag L. monocytogenes strains, with a particular emphasis on the development of multiple strain competitive index assays.     

A survey of intracellular Na+ and K+ of various normal,transformed, and tumor cells

Intracellular concentrations of Na⁺ and K⁺ of various normal, transformed, and tumor cell cultures were analyzed by atomic absorption spectrophotometry. In all of the cultures analyzed there were markedly different concentrations in the transformed and tumor cells when compared to their normal counterparts. Although increased Na⁺ was often observed, there were no definitive correlations between absolute ion concentrations, or Na⁺:K⁺ ratios, and cell transformation.     

Analysis of the compartments of the wing of Drosophila melanogaster mosaic for a temperature-sensitive mutation that reduces mitotic rate

Gynandromorphs of Drosophila melanogaster were analysed in which the female tissue was normal but the male tissue was hemizygous for a temperature-sensitive mutation, l(1)ts1126, which reduces mitotic rate. In gynandromorphs grown at restrictive temperature, the slow-growing l(1)ts1126 tissue survives preferentially when it is segregated from the wild-type tissue, i.e., when it occupies an entire imaginal disc or an entire anterior or posterior compartment within a disc. Mosaic compartments composed of both male, l(1)ts1126, and female wild-type tissue are found less frequently at restrictive temperature than at permissive temperature and when present, are composed mainly of wild-type tissue with very small patches of l(1)ts1126. These very small patches are found almost exclusively along the borders defining compartments. The implications of these results to theories concerning the way in which the compartment boundaries may be maintained is considered. In gynandromorphs grown at restrictive temperature, the size of compartments composed entirely of l(1)ts1126 tissue is drastically reduced, relative to those composed of wild-type tissue. The observations support the hypothesis that the sizes of the anterior and posterior compartments are autonomously controlled.     

A Semi-Automated Single Day Image Differencing Technique to Identify Animals in Aerial Imagery

Our research presents a proof-of-concept that explores a new and innovative method to identify large animals in aerial imagery with single day image differencing. We acquired two aerial images of eight fenced pastures and conducted a principal component analysis of each image. We then subtracted the first principal component of the two pasture images followed by heuristic thresholding to generate polygons. The number of polygons represented the number of potential cattle (Bos taurus) and horses (Equus caballus) in the pasture. The process was considered semi-automated because we were not able to automate the identification of spatial or spectral thresholding values. Imagery was acquired concurrently with ground counts of animal numbers. Across the eight pastures, 82% of the animals were correctly identified, mean percent commission was 53%, and mean percent omission was 18%. The high commission error was due to small mis-alignments generated from image-to-image registration, misidentified shadows, and grouping behavior of animals. The high probability of correctly identifying animals suggests short time interval image differencing could provide a new technique to enumerate wild ungulates occupying grassland ecosystems, especially in isolated or difficult to access areas. To our knowledge, this was the first attempt to use standard change detection techniques to identify and enumerate large ungulates.     

Specific cellular expression of monoamine oxidase B during early stages of quail embryogenesis

Monoamine oxidase-B (MAO-B) is one of two distinct molecular forms of MAO that in part regulate the cellular levels of biogenic amines. In order to determine whether discrete cell populations known to express aminergic properties in the vertebrate embryo also express MAO-B, the distribution of MAO-B-immunoreactive cells was examined in early developing quail embryos. Two major patterns of staining emerge. First, tissues known to express several aminergic characteristics are initially MAO-B positive at early stages of development and continue to express immunoreactivity through Zacchei stage 20, the oldest stage examined. These include cells of the sympathetic and some cranial and trunk sensory ganglia (beginning at stage 13), the pancreas (stage 14), and the brain stem raphe (stage 14). Second, other structures that contain or accumulate biogenic amines are transiently MAO-B immunopositive during early stages of development. These tissues include extraembryonic yolk sac and presumptive gut endoderm (with most intense staining between stages 8 and 13), the ventral trunk neural tube (stages 14 and 16), and the notochord (stages 8–10). MAO-B immunoreactivity disappears from these regions at different stages, and none are MAO-B positive by stage 19–20. Other structures without known aminergic properties during early development also stain; these include liver (stage 20), mesenchymal cells that surround the Wolffian duct and lung buds (stages 14 and 18), and endothelial cells surrounding the dorsal aorta (stages 14 and 20). In general, however, MAO-B appears to be distributed in embryonic tissues that can use this enzyme to regulate biogenic amine levels either transiently or during initial phenotypic expression of aminergic traits.     

Costs and benefits of a community special care baby service

Between January 1981 and December 1986 3829 low birthweight (<2500 g) infants and 1980 other high risk infants were cared for at home after they were discharged from hospital by a specialist neonatal nursing service. Of the infants who were referred to this service, 720 (12%) weighed under 2000 g and 1919 (33%) under 2250 g at the time of discharge home. The infants were visited by the community neonatal sisters on an average of 11 occasions, but the number of visits varied from six to over 100 depending on the needs of the child and parents. There was close liaison with other community and hospital staff. Two hundred and thirty (4%) referred infants were readmitted to hospital while under the care of the specialist nursing service. In 1985 the cost of the service was £127 000, or £123 for each infant referred. Providing this specialist support at home allowed much earlier discharge of low birthweight infants from hospital. When compared with the cost of providing continuing inpatient neonatal care earlier discharge was estimated to have saved roughly £250 000 in 1985.Low birthweight infants have an increased risk of serious illness or death that extends beyond the neonatal period. Many are born to young and socially disadvantaged parents who can benefit from expert guidance and support at home. A community neonatal nursing service has advantages for high risk infants and their parents, is cost effective, and allows more efficient use of limited hospital resources.     

Spatial variation in selection in a plant-pollinator system in the wadis of Sinai,Egypt

We studied an insect-plant pollination system in adjacent steep-sided wadis and a connecting plain in the mountains of southern Sinai (Egypt): this environment creates a strongly divided habitat, which may promote the local differentiation of sub-populations. We tested for spatial differences in phenotypic reproductive characters of the only plant flowering abundantly in early spring, Alkanna orientalis (Boraginaceae), and its major pollinator at that time of year, Anthophora pauperata (Apoidea, Anthophoridae). There were significant morphological differences between sub-populations of Alkanna, mainly between plants from the narrower wadis and those on the interconnecting plain. Flowers on the plain were larger, with wider corollas and more nectar standing crop; these plants retained more flowers on the inflorescence, but received many fewer visits to flowers. There was a significant selection gradient between flower size and maternal fitness (seed set) in the plain, but not elsewhere. Natural selection may have increased resources devoted to attracting insect visitors in response to fewer pollinating visits in the plain. Consistent with this explanation, by experimentally manipulating flower number per plant, we showed that within a wadi having more flowers on a plant secured more visits.     

Responses to T cell receptor/CD3 and interleukin-2 receptor stimulation are altered in T cells from B cell non-hodgkin's lymphomas

T cells infiltrating (T-TIL) B cell non-Hodgkin's lymphomas (NHL) are thought to represent a local host response to the tumor. However, tumor progression in the presence of this T cell infiltrate suggests that the T-TIL may be functionally impaired. To address this issue we determined whether response to stimulation of T-TIL from 25 patients with NHL through the T cell receptor (TCR/CD3) and the interleukin-2 (IL-2) receptor (IL-2R) was intact, since activation of these receptors is important for proliferation and cytokine production. Our results demonstrate defects in response to stimulation via TCR/CD3 and the IL-2R in T-TIL cells from patients with NHL that were not observed with T cells from the peripheral blood. T-TIL showed minimal proliferation to anti-CD3 and only modest proliferation to IL-2 alone or when combined with anti-CD3. Moreover, cytokine production in T-TIL was impaired since stimulation through the TCR/CD3 complex did not induce mRNA for interferon (IFN), IL-2, IL-4 or IL-10. The functional unresponsiveness of these cells may be linked to altered signalling through the TCR/CD3 since an abnormal tyrosine phosphorylation pattern was detected in T-TIL after stimulation with anti-CD3.