Injury and recovery of Spirogyra exposed to ultrasound

• 1.1. The time course of morphological changes in Spirogyra exposed to ultrasound is as follows:There is an initial rate of appearance of injury which increases with ultrasound power input.At relatively low power inputs the degree of injury reaches a maximum within 5 to 15 minutes and there is then a partial recovery to a level which is maintained for an hour or more. Eventually further damage may occur.At high power inputs there is no maximum and all cells are irreversibly injured or killed within a short time.
• 2.2. Pre-exposure of Spirogyra specimens to a level of ultrasound which produces no visible change has a marked inhibiting effect on the production of injury by a subsequent exposure to more intense ultrasound.
• 3.3. Recovery of reversibly damaged cells removed from the ultrasound field is very slow compared with changes occurring during exposure.
• 4.4. Near 23 °C, the injury produced by a given sound field is a minimum and the partial recovery during exposure is a maximum. At higher and lower temperatures, the cells are less resistant to injury and recover less.
• 5.5. Ethyl ether added to the exchange medium in small amounts reduces both the degree of damage and the degree of partial recovery.
• 6.6. A discussion of the general characteristics of injury and recovery of cells under the influence of noxious stimuli leads to a formulation of the processes in terms of a second order, non-linear differential equation the solution of which reproduces certain general characteristics of the system fairly well.