Lecture notes for Monday, February 18
Chemotaxis
Accumulation of cells in a specific place can be either by selective adhesiveness ("haptotaxis") or by chemotaxis.Scientists tend to think of chemotaxis as ONE mechanism, But bacterial chemotaxis is by an increase in random turning when the attractant concentration decreases.
Leucocyte & Dictyostelium chemotaxis is by turning of locomotion toward the side where there is a higher concentration of attractant.
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video of Dictyostelium amoebae aggregating to form slugs
video of small ciliates responding to a dying larger ciliate
Two mechanisms of chemotaxis
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Two videos of computer simulations of mechanisms of chemotaxis, with narration.
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first video: demonstration of behavioral rules that can produce the effects of chemotaxis
second video: user's choice of different rules
Chemotaxis of a chick dorsal root axon toward a pipette containing nerve growth factor;
based on a classic paper by Gundersen and Barrett, 1979