Novel Dopamine Therapeutics for Cognitive Deficits in Schizophrenia

Schizophrenia is characterized by profound cognitive deficits that are not alleviated by currently available medications. Many of these cognitive deficits involve dysfunction of the newly evolved, dorsolateral prefrontal cortex (dlPFC). The brains of patients with schizophrenia show evidence of dlPFC pyramidal cell dendritic atrophy, likely reductions in cortical dopamine, and possible changes in dopamine D1 receptors (D1R). It has been appreciated for decades that optimal levels of dopamine are essential for dlPFC working memory function, with many beneficial actions arising from D1R stimulation. D1R are concentrated on dendritic spines in the primate dlPFC, where their stimulation produces an inverted-U dose response on dlPFC neuronal firing and cognitive performance during working memory tasks. Research in both academia and the pharmaceutical industry has led to the development of selective D1 agonists, e.g., the first full D1 agonist, dihydrexidine, which at low doses improved working memory in monkeys. Dihydrexidine has begun to be tested in patients with schizophrenia or schizotypal disorder. Initial results are encouraging, but studies are limited by the pharmacokinetics of the drug. These data, however, have spurred efforts toward the discovery and development of improved or novel new compounds, including D1 agonists with better pharmacokinetics, functionally selective D1 ligands, and D1R positive allosteric modulators. One or several of these approaches should allow optimization of the beneficial effects of D1R stimulation in the dlPFC that can be translated into clinical practice.

Agricultural science in the wild: a social network analysis of farmer knowledge exchange

Responding to demands for transformed farming practices requires new forms of knowledge. Given their scale and complexity, agricultural problems can no longer be solved by linear transfers in which technology developed by specialists passes to farmers by way of extension intermediaries. Recent research on alternative approaches has focused on the innovation systems formed by interactions between heterogeneous actors. Rather than linear transfer, systems theory highlights network facilitation as a specialized function. This paper contributes to our understanding of such facilitation by investigating the networks in which farmers discuss science. We report findings based on the study of a pastoral farming experiment collaboratively undertaken by a group of 17 farmers and five scientists. Analysis of prior contact and alter sharing between the group's members indicates strongly tied and decentralized networks. Farmer knowledge exchanges about the experiment have been investigated using a mix of quantitative and qualitative methods. Network surveys identified who the farmers contacted for knowledge before the study began and who they had talked to about the experiment by 18 months later. Open-ended interviews collected farmer statements about their most valuable contacts and these statements have been thematically analysed. The network analysis shows that farmers talked about the experiment with 192 people, most of whom were fellow farmers. Farmers with densely tied and occupationally homogeneous contacts grew their networks more than did farmers with contacts that are loosely tied and diverse. Thematic analysis reveals three general principles: farmers value knowledge delivered by persons rather than roles, privilege farming experience, and develop knowledge with empiricist rather than rationalist techniques. Taken together, these findings suggest that farmers deliberate about science in intensive and durable networks that have significant implications for theorizing agricultural innovation. The paper thus concludes by considering the findings' significance for current efforts to rethink agricultural extension.

DNA Extraction and PCR Methods for the Detection of Listeria monocytogenes in Cold-Smoked Salmon

Protocols for the specific detection of Listeria monocytogenes in cold-smoked salmon were developed. PCR was used as the method of detection. Inhibitors of PCR present in the food samples were removed by ether extraction or column purification, or their effect was overcome by the use of Tween 20 as an enhancer. These protocols are many times more rapid than conventional detection methodologies and also have the potential for automation.

A rapid general method for the identification of PCR products using a fibre-optic biosensor and its application to the detection of Listeria

A 200-mer fragment of the flaA gene from Listeria monocytogenes was amplified using the polymerase chain reaction (PCR) incorporating biotin- and fluorescein amadite (FAM-)labelled primers. Methods are described for isolating the single stranded FAM-labelled 200-mer. A central portion of this 200-mer was successfully hybridized onto a complementary sequence coated onto a fibre optic biosensor. Advantages in the specificity and speed of this approach compared to standard agarose gel electrophoresis and probing methods are discussed.

Rapid RAPD analysis for distinguishing Listeria species and Listeria monocytogenes serotypes using a capillary air thermal cycler

Using a novel capillary thermal cycler, randomly amplified polymorphic DNA (RAPD) generated DNA fingerprints were obtained in 3 h. The RAPD profiles were produced using a random 10-mer primer (5'-ACCGCCTGCT-3') which discriminated between different Listeria spp. Unique fragment profiles of Listeria monocytogenes serotypes were produced from serotypes 1a, 2, 3a, 4ab, 4a and 4c but serotypes, 1/2a, 4b, 4d and 7 had similar profiles.

Polymerase chain reaction amplification of the flaA gene for the rapid identification of Listeria spp

The polymerase chain reaction was used to amplify specifically a 448 base pair internal fragment of the flaA gene from bacteria belonging to the genus Listeria. This gene encodes for the flagellin protein and allowed specific genus discrimination between other commonly found Gram-positive and Gram-negative bacteria and all Listeria spp. with the exception of Jonesia denitrificans.

Apical hyphal extension in Streptomyces coelicolor A3(2)

Hyphal extension in the filamentous actinomycete Streptomyces coelicolor A3(2) was shown to occur by addition of newly synthesized wall material in an apical extension zone. Incubation of mycelia with tritiated N-acetyl-D-glucosamine (GlcNAc), a precursor of peptidoglycan, resulted in localized incorporation of label at the apex, as indicated by light microscopic and electron microscopic autoradiography. Within the hyphal extension zone there was a sharp decrease in incorporation with increasing distance from the apex. Hyphal tip shape, examined by low-temperature scanning electron microscopy, approximated to a semi-ellipsoid of revolution and was not hemispherical. Tip shape could be represented accurately by polynomial equations of degree less than seven. The surface stress theory was successfully applied to hyphal tip growth, with tip shape related qualitatively to the inverse of surface tension within the wall of the extension zone. Surface tension was assumed to be inversely proportional to the rate of incorporation of tritiated GlcNAc. Treatment of surface-grown hyphae with beta-lactam antibiotics resulted in localized swelling of hyphal tips. Lysozyme caused swelling of tips and of other regions of hyphae, frequently giving a beaded morphology associated with septa.