IRS-2 Deficiency Impairs NMDA Receptor-Dependent Long-term Potentiation

The beneficial effects of insulin and insulin-like growth factor I on cognition have been documented in humans and animal models. Conversely, obesity, hyperinsulinemia, and diabetes increase the risk for neurodegenerative disorders including Alzheimer's disease (AD). However, the mechanisms by which insulin regulates synaptic plasticity are not well understood. Here, we report that complete disruption of insulin receptor substrate 2 (Irs2) in mice impairs long-term potentiation (LTP) of synaptic transmission in the hippocampus. Basal synaptic transmission and paired-pulse facilitation were similar between the 2 groups of mice. Induction of LTP by high-frequency conditioning tetanus did not activate postsynaptic N-methyl-D-aspartate (NMDA) receptors in hippocampus slices from Irs2−/− mice, although the expression of NR2A, NR2B, and PSD95 was equivalent to wild-type controls. Activation of Fyn, AKT, and MAPK in response to tetanus stimulation was defective in Irs2−/− mice. Interestingly, IRS2 was phosphorylated during induction of LTP in control mice, revealing a potential new component of the signaling machinery which modulates synaptic plasticity. Given that IRS2 expression is diminished in Type 2 diabetics as well as in AD patients, these data may reveal an explanation for the prevalence of cognitive decline in humans with metabolic disorders by providing a mechanistic link between insulin resistance and impaired synaptic transmission

Biological Control of Postharvest Diseases of Fruit: Inhibition Of Botrytis Rot On Apple by an Antagonistic Yeast

As an alternative to fungicides, biological control of postharvest diseases of fruit has recently met with good success with peaches and apples and is an area of great potential. In contrast to previous study, we were particularly interested in finding antagonists that did not produce antibiotics as part of their mode of action. After extensive screening, several yeast and bacteria were identified that exhibited biocontrol of a number of postharvest disease organisms. In particular, the yeast, Debaryomyces hansenii, indicated great potential as a biocontrol agent without exhibiting antibiotic production as a mode of action. It has been recently shown to effectively control decay on citrus caused by Penicillium digitatum, Penicilliim italicum and Geotrichum candidum. The present report is the first to document the use of D. hansenii to control postharvest decay of apples by Botrytis cinerea and present possible inodes of action.To test for biocontrol activity, apples (cv Golden Delicious) ware wounded with a 4 nm cork borer to a depth of 5 mm.</jats:p