Goldschmidt staining of auditory cortical fields - the new method of Thallium autometallography applied around onset of hearing in juvenile Mongolian gerbils (Meriones unguiculatus)

Investigations on the development of functional activity in the auditory cortex (AC) of non-human mammals give insights into the principles of map formation. The plasticity of cortical maps suffered from auditory deprivation was already described with Fluoro-2-deoxyglucose (FDG) in domesticated Gerbils (Meriones unguiculatus forma domestica ). A new method to map functional activity, named Thallium (TL) autometallography, was recently developed by Goldschmidt . Here, we apply this technique in juvenile gerbils to visualize map formation around hearing onset.TL autometallography is based on the tight coupling of neuronal activity and potassium K+ uptake. Neurons have to compensate for the loss of potassium, TL as its analogue accumulates in active cells. TL distribution in cortical layers could be mapped with staining based on silver intensification of heavy metal sulphides . Onset of hearing in gerbils takes place around postnatal day 14. Specimen between P11 and P17 were injected with 50-200 µl of the K+ analogue TL i.p. and kept without further sensory stimulation. Brains were removed, frozen and sectioned (25 µm). Neuronal activity marked by TL was compared with activity patterns obtained by the FDG method. TL applied to juveniles gave sufficient visualisation of cortical activity, including the spatial resolution of cortical columns. Prominent activity in the primary auditory field (A1) and the anterior auditory field (AAF) were evident in TL as well as in FDG images. Methodological restrictions arose neither from small hearts perfused (<100 mg) nor from histology in premature brains. Ongoing research should allow the visualization of neuronal activity with cellular resolution

Wild-derived mouse stocks: an underappreciated tool for aging research

Virtually all biomedical research makes use of a relatively small pool of laboratory-adapted, inbred, isogenic stocks of mice. Although the advantages of these models are many, there are a number of disadvantages as well. When studying a multifaceted process such as aging, the problems associated with using laboratory stocks are greatly inflated. On the other hand, wild-derived mouse stocks, loosely defined here as either wild-caught individuals or the recent progeny of wild-caught individuals, have much to offer to biogerontology research. Hence, the aims of this review are threefold: (1) to (re)acquaint readers with the pros and cons of using a typical inbred laboratory mouse model for aging research; (2) to reintroduce the notion of using wild-derived mouse stocks in aging research as championed by Austad, Miller and others for more than a decade, and (3) to provide an overview of recent advances in biogerontology using wild-derived mouse stocks

<Note>Some Professional and Technical Occupations in the Republic of Vietnam

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