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Biomedical subjects

I M Scott

Publications and source records attributed to I M Scott.

At least 19 recordsLinked to original sources
PubMed2004

Modification of senescence in ryegrass transformed with IPT under the control of a monocot senescence-enhanced promoter.

We report here the genetic modification of ryegrass senescence. Embryogenic cell suspensions of Lolium multiflorum were transformed by microprojectile bombardment with plasmid constructs containing 1.98 kb of the 5' flanking sequence of SEE1 (a maize cysteine protease gene showing enhanced expression during senescence) fused either to the Agrobacterium tumefaciens cytokinin biosynthesis gene IPT (designated PSEE1::IPT) or to the beta-glucuronidase reporter gene UIDA (PSEE1::UIDA). Plants were regenerated under selection for the HPH hygromycin resistance gene in the vector. PSEE1::UIDA transformants confirmed that the SEE1 flanking sequence functioned as a senescence-enhanced promoter in ryegrass. The IPT transgene was detected in 28 regenerants (PSEE1::IPT) from five independent transformation events. PSEE1::IPT leaves displayed a stay-green phenotype. Some PSEE1::IPT lines developed spontaneous lesions.

Aging↗
PubMed2004

Efficacy of Piper (Piperaceae) extracts for control of common home and garden insect pests.

Extracts from three species of the plant family Piperaceae, Piper nigrum [L.], Piper guineense [Schum & Thonn, and Piper tuberculatum [Jacq.], were tested for efficacy against insects from five orders. All three species contain isobutyl amides, plant secondary compounds that act as neurotoxins in insects. These materials are considered safe to mammals because Piper spp. were used for centuries for spice and medicinal purposes. When 24-h P. nigrum LC50 values were compared between common insect pests from eastern Canada and the northeastern United States, the most sensitive species in order of increasing lethal concentration were eastern tent caterpillar, Malacosoma americanum (F.) < European pine sawfly larvae, Neodiprion sertifer (Geoffroy) < spindle ermine moth larvae, Yponomeuta cagnagella [Hübner] < viburnum leaf beetle larvae, Pyrrhalta viburni [Paykull] < stripped cucumber beetle adults, Acalymma vittatum (F.) < Colorado potato beetle adults, Leptinotarsa decemlineata (Say) < Japanese beetle adults, Popillia japonica [Newman] < hairy chinch bug, Blissus leucopterus hirtis [Montandon]. The life stage tested was the point at which each species causes the greatest amount of damage to the host plant and the point at which most gardeners would likely choose to treat with a conventional synthetic insecticide. Greenhouse trials revealed that the pepper formulations also had a repellent activity, thus protecting plant leaves from 1) herbivory (lily leaf beetle, Lilioceris lilii [Scopoli], adults and larvae and stripped cucumber beetle adults) and 2) oviposition [European corn borer, Ostrinia nubilalis (Hübner)]. Combinations with other botanical extracts were additive at best in toxicity and repellent trials. Nontarget toxicity to beneficial invertebrates is a possibility because the P. nigrum LC50 for beneficial ladybird beetles was 0.2%. P. nigrum extracts can provide a reasonable level of control against lepidopteran and European pine sawfly larvae and also will work as a short-term repellent and feeding deterrent. It is recommended that the use of Piper extracts be restricted to small-scale spot treatments in residential areas where insect pest outbreaks have occurred.

Animals↗
PubMed2003

Botanical insecticides for controlling agricultural pests: piperamides and the Colorado Potato Beetle Leptinotarsa decemlineata say (Coleoptera: Chrysomelidae).

The efficacy of extracts from two Piperaceae species, Piper nigrum L. and P. tuberculatum Jacq. were evaluated using larvae and adults of the Colorado Potato Beetle Leptinotarsa decemlineata (Say). Young larvae and neonates were the most susceptible; a 24-h LD(50) of 0.064% extract of P. tuberculatum was determined for 4-day-old larvae, while 0.05% extract of P. nigrum reduced larval survival up to 70% within one week after treatment of potato Solanum tuberosum L. (Solanaceae) plants. When an insecticide resistant strain of L. decemlineata larvae was tested with the P. tuberculatum extract, there was less than a 2-fold tolerance ratio compared to the 22-fold tolerance ratio to cypermethrin, a pyrethroid. Older larvae, pre-pupal stage and adults, were less sensitive to the P. nigrum extracts; the 24-h LD(50) was 0.5% (95% C.I. = 0.36, 0.65). However, the same concentration was equally effective under field conditions. In the greenhouse, P. nigrum at 0.5% was as effective at reducing adult L. decemlineata feeding as combinations with 2 separate botanical mixtures, garlic and lemon grass oil. Under field conditions, the residual activity of the P. nigrum extracts was less than 3 h. When adult L. decemlineata were placed on treated plants exposed to full sunlight for 0, 1.5, and 3 h, leaf damage progressively increased as the main active compound, piperine, was found to degrade by 80% after 3 h. An in vitro polysubstrate monoxygenase (PSMO) enzyme assay, using the substrate methoxyresorufin O-demethylation (MROD), determined that the principal P. nigrum active compound, piperine, is responsible for inhibition of that specific enzyme. The results suggest that Piper extracts could be used effectively as contact botanical insect control agents to protect potato plants from developing L. decemlineata larvae at concentrations less than 0.1%. There is also potential for Piper extracts to control insecticide resistant populations in conjunction with other integrated pest management (IPM) strategies used in conventional and organic agriculture.

Agriculture↗
PubMed2003

Improving appearance model matching using local image structure.

We show how non-linear representations of local image structure can be used to improve the performance of model matching algorithms in medical image analysis tasks. Rather than represent the image structure using intensity values or gradients, we use measures that indicate the reliability of a set of local image feature detector outputs. These features are image edges, corners, and gradients. Feature detector outputs in flat, noisy regions tend to be ignored whereas those near strong structure are favoured. We demonstrate that combinations of these features give more accurate and reliable matching between models and new images than modelling image intensity alone. We also show that the approach is robust to non-linear changes in contrast, such as those found in multi-modal imaging.

Algorithms↗
PubMed2000

Inhibition of glutathione S-transferases (GSTs) from parasitic nematodes by extracts from traditional Nigerian medicinal plants.

Piliostigma thonningii, Ocimum gratissimum, Nauclea latifolia and Alstonia boonei are used in Nigerian traditional medicines against gastrointestinal helminths of animals and man. Proanthocyanidins were detected in Piliostigma and Nauclea, but not Alstonia or Ocimum. Extracts of these plants killed 50% of brine shrimp nauplii at <10 ppm (Nauclea), 100 ppm (Piliostigma) and <1000 ppm (Ocimum and Alstonia), the Nauclea LD50 being similar to the anthelmintic drug piperazine. Extracts were also toxic to the parasitic nematode Haemonchus infective L3 stage. Nematode glutathione-S-transferases (GSTs) are potential drug targets. Apart from Alstonia all the medicinal plants contained heat-stable inhibitory activities against recombinant Ascaris and Onchocerca GSTs in vitro. Piliostigma, Ocimum and Nauclea had IC50s of 2, 10 and 15 microg/mL respectively for Ascaris GST and 4, 8, 28 microg/mL respectively for Onchocerca GST. We suggest that the inhibitory properties of some of these Nigerian plant extracts against GST may contribute to the pharmacological basis of their efficacy against helminths in traditional herbal use.

Animals↗
PubMed2000

The toxicity of a neem insecticide to populations of culicidae and other aquatic invertebrates as assessed in in situ microcosms.

Microcosm trials were conducted with the botanical insecticide Margosan-O(R) to assess the potential hazards of the product to aquatic organisms. Laboratory chronic bioassays with water from the treated microcosms were conducted to provide an estimate of the residual effect of Margosan-O. Results from chronic tests showed Margosan-O toxicity to be greater in the laboratory exposures than in situ with Culicidae larvae exposed to the same concentrations. Residue analyses of the active ingredient, azadirachtin, determined that it had a half-life of 36 to 48 h in water exposed to natural sunlight. Two applications of Margosan-O at the recommended application rate for pests did not harm aquatic invertebrates that are categorized as planktonic and filter feeding (Culex sp. and Daphnia sp.). However, the benthic invertebrate (Chironomus riparius) was affected by multiple applications of neem. These results show that the use of Margosan-O and possibly other neem extracts in or near aquatic environments could lead to disturbances in benthic populations and may cause decreases in numbers of organisms that are important in food web and nutrient cycling processes.

Animals↗
PubMed1997

Expression of the abnormal gravitropism phenotypes creep and ageotropum during development in pea.

This study established that the mutant creep and ageotropum phenotypes are expressed differently during development in pea (Pisum sativum L.). Etiolated ageotropum stems grew at a wide range of angles, whereas etiolated creep stems emerged vertically from the compost. However, when etiolated creep stems were subjected to additional gravitropic demands, such as growth to excessive height or reorientation, abnormality was detectable. When plants were handled to a greater extent, earlier loss of vertical growth resulted. In light-grown shoots, creep lost vertical orientation, whereas ageotropum grew more normally. Root systems of creep exhibited normal growth patterns, whereas ageotropum main and lateral roots grew at abnormal angles. Thus, the ageotropum mutation strongly affects gravitropism in roots and etiolated stems, whereas the creep mutation affects both light- and dark-grown stems, but is most apparent in older, taller plants.

Darkness↗
PubMed1993

Expression of the UNC-5 guidance receptor in the touch neurons of C. elegans steers their axons dorsally.

Growth cones in developing nervous systems encounter a sequence of extracellular cues during migration. In theory, a growth cone can navigate by selectively expressing or activating surface receptor(s) that recognize extracellular cues appropriate to each migratory phase. Using the simple Caenorhabditis elegans nervous system, we attempted to demonstrate that path selection by migrating growth cones can be predictably altered by ectopic expression of a single receptor. The unc-5 gene of C. elegans encodes a unique receptor of the immunoglobulin superfamily (UNC-5), required cell-autonomously to guide growth cone and mesodermal cell migrations in a dorsal direction on the epidermis. We report here that the UNC-5 receptor induces dorsally oriented axon trajectories when ectopically expressed in the touch receptor neurons which normally extend pioneer axons longitudinally or ventrally on the epidermis. These errant trajectories depend on unc-6, which encodes a putative epidermal path cue, just as normal dorsally oriented axon trajectories do (such as those of certain motor neurons), suggesting that UNC-5 acts to reorient the touch cell growth cones by using its normal guidance mechanisms. These results support previous evidence that UNC-5 and UNC-6 play instructive rules in guiding growth cone migrations on the epidermis in C. elegans, and indicate that pioneering growth cones, which normally migrate in different directions, may use equivalent intracellular signalling mechanisms for guidance.

Animals↗
PubMed1992

The mec-7 beta-tubulin gene of Caenorhabditis elegans is expressed primarily in the touch receptor neurons.

Mutants of the mec-7 beta-tubulin gene of Caenorhabditis elegans lack the large diameter 15-protofilament microtubules normally found only in the set of six touch receptor neurons. Both a mec-7-lacZ reporter gene and affinity-purified anti-mec-7 antibodies were used to show that mec-7 is expressed primarily in the touch neurons. These data are consistent with a possible instructive role for the mec-7 tubulin in determining microtubule protofilament number. The antibodies and the mec-7-lacZ transgene were also used to examine mec-7 expression in mutants affecting the generation, differentiation or maintenance of the touch neurons. Decreased expression was observed in mutants of unc-86 and mec-3, genes that encode transcription factors essential for touch receptor neuron generation and differentiation, respectively.

Amino Acid Sequence↗
PubMed1990

Genetic and molecular analysis of vgU and vgW: two dominant vg alleles associated with gene fusions in Drosophila.

In the absence of a vg+ gene, extensive cell death occurs in third instar imaginal discs, which results in a complete loss of adult wing margin structures. Essentially all molecularly characterized vg alleles are associated with deletions or insertions of DNA into the vg locus. These alterations reduce or eliminate a 3.8-kb vg-specific transcript, resulting in recessive loss of function alleles. We report here the analysis of two dominant vg alleles which have been identified (vgU and vgW). The vgU allele is associated with a chromosomal inversion which splits the vg locus, resulting in a gene fusion between vg and the mastermind (mam) neurogenic locus. Reversion analysis of vgU indicates that sequences from the mam locus are required for vgU dominance. The vgW allele is also the result of a chromosomal inversion, in this case resulting in a gene fusion between vg and the homeobox-containing invected (inv) gene. It is also associated with novel dominant homeotic transformations. Revertant analysis indicates that sequences from inv are required for the dominant wing and dominant homeotic effects of vgW. The vg dominance does not appear to be mediated through a reduction of vg expression or a novel fusion transcript in either vgU or vgW. The results are consistent with a model in which inappropriate expression of inv causes the dominant homeotic effects seen in vgW.

Alleles↗
PubMed1987

Leukocytic pyrogen effects on prostaglandins in hypothalamic tissue slices.

Some studies suggest that leukocytic pyrogen (LP) increase hypothalamic prostaglandins which, in turn, affect hypothalamic thermoregulatory neurons to produce fever. The present study used radioimmunoassays to quantitate the ability of guinea pig hypothalamic tissue slices to produce prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TxB2). Dose- and time-dependent prostaglandin increases occurred when these slices were perfused with LP media. Steady-state levels of tissue release were reached at 0-3 min for 6-keto-PGF1 alpha, at 6-9 min for PGE2 and PGF2 alpha, and at 12-15 min for TxB2. With the exception of 6-keto-PGF1 alpha, all substances showed continuous dose-response relationships for concentrations ranging from 0.001 to 0.25 LP dilutions. Tissue PGE2, for example, was 0.7 pg X min-1 X mg-1 with the 0.001 LP dilution and 8.7 pg X min-1 X mg-1 with the 0.25 LP dilution. Indomethacin blocked much of the LP-induced prostaglandin increase. Although there is a relationship between hypothalamic LP and prostaglandins in response to physiological LP levels, tissue prostaglandins are several orders of magnitude lower than concentrations necessary to produce fever by hypothalamic microinjection. This suggests that prostanoids, such as PGE2, may not be the sole mediators of fever induced by leukocytic pyrogen.

Animals↗
PubMed1984

Dopamine effects on thermosensitive neurons in hypothalamic tissue slices.

To understand the role of hypothalamic dopamine in thermoregulation, single unit activity was recorded in vitro, from constantly perfused tissue slices of rat preoptic area and anterior hypothalamus, PO/AH. The firing rate and thermosensitivity of individual PO/AH neurons were determined before, during and after tissue perfusion with media containing dopamine. Dopamine excited 41% of the warm-sensitive neurons, inhibited 100% of the cold-sensitive neurons, and had no effect on 83% of the temperature-insensitive neurons. In addition, dopamine decreased the local thermosensitivity of most cold-sensitive neurons. There were no major differences between these neuronal types in terms of the time course or latency of dopamine's effect. These results are consistent with the hypothesis that dopamine is involved in hypothalamic synapses controlling thermoregulatory responses which oppose increases in body temperature.

Animals↗