Donald J. Donaldson

Influence of catecholamines on epidermal cell migration during wound closure in adult newts

Following removal of a skin patch from each hind limb of a series of adult newts, the limbs were explanted into small dishes of Holtfreter solution containing various combinations of test drugs. Later, the amount of wound epithelium that formed on each limb was determined using a planimeter on wound tracings obtained with the aid of a drawing tube-equipped microscope. All three (-)-catecholamines tested inhibited migration with the following order of effectiveness: isoproterenol greater than epinephrine greater than norepinephrine. The effect was stereospecific with (-)-isoproterenol clearly more effective than the (+)-isomer. Propranolol, a beta antagonist, blocked the effect of (-)-isoproterenol while the alpha antagonist, phentolamine, was less effective. One hour in (-)-isoproterenol inhibited migration to the same degree as continuous exposure for the 6 hr most experiments were allowed to run. Taken together, the data suggest that catecholamines exert their effect on epidermal cell migration via beta 2 adrenergic receptors on the cell surface, a binding site which implicates cAMP in the chain of events.

Inability of colchicine to inhibit newt epidermal cell migration or prevent concanavalin A-mediated inhibition of migration. Studies in vivo.

Abstract Adult newts injected with metaphase-accumulating doses of colchicine showed no inhibition of epidermal cell migration during wound closure, indicating that microtubules are unnecessary for locomotion of these epithelial cells. Neither could colchicine alter ConA-induced inhibition of migration, indicating further that there is no microtubule requirement for this phenomenon.

Epidermal cell migration on laminin-coated substrates

SummaryPieces of coverslip glass coated with various proteins were implanted under one edge of a fresh skin wound on adult newt hind limbs so that the implant served as wound bed for the migrating wound epithelium. Laminin, a protein that has been implicated as an epithelial-specific adhesin, was a moderately good migration substrate. Type-IV collagen, fibrinogen and fibronectin, however, were significantly better. Fetuin, myoglobin, and casein all proved to be very poor substrates, allowing practically no migration. The inability of fetuin, myoglobin, and casein to support migration is further evidence that the considerable migration that occurs on collagen (Donaldson et al. 1982) fibrinogen and fibronectin (Donaldson and Mahan 1983) and the moderate migration on laminin, is a relatively specific response to these proteins and is therefore of special significance. The fact that laminin is a poorer migration substrate than collagen, fibrinogen or fibronectin suggests that the absence of cell surface laminin that has been associated with epithelial movement in several studies (Stanley et al. 1981; Clark et al. 1982; Madri and Stenn 1982; Gulati et al. 1983) may promote motility by allowing epithelial cells to interact directly with other extracellular macromolecules.

Early events following amputation of adult newt limbs given regeneration inhibitory doses of X irradiation

Abstract X irradiation, (2000 R) prevented regeneration but had no apparent effect on morphological dedifferentiation. DNA synthesis and mitotic activity increased significantly in irradiated limbs after amputation but not as much as in regenerating unirradiated controls. Even though fewer mitotic cells were seen in irradiated limbs, those that occurred were distributed normally throughout the stump. The results indicate that morphological dedifferentiation and entry into the cell cycle are dissociable events and that X rays act by interfering with the latter. They also show that some cells in irradiated amputated limbs not only synthesize DNA but also divide.

Effects of concanavalin a and cholera toxin on epidermal cAMP and migration rate during wound closure in adult newts

Following removal of a skin patch from each hind limb of a series of adult newts, the limbs were explanted into small dishes of Holtfreter solution containing various combinations of test drugs. Later, the amount of wound epithelium that formed on each limb was determined using a planimeter on wound tracings obtained with the aid of a drawing tube-equipped microscope. Exposure of migrating cells to the plant lectin, concanavalin A (con A), lowered cyclic AMP (cAMP) levels and depressed migration. Exposure to cholera toxin and theophylline (CTX) significantly elevated cAMP levels and significantly depressed migration rate. Exposure of CTX-treated cells to con A tended to lower CTX-elevated cAMP levels while depressing the migration rate well beyond the depression caused by CTX alone. These results provide further evidence that cAMP can regulate the rate of newt epidermal cell migration. They also show that the inhibitory effect of con A on motility in these cells is independent of its effects on cAMP.

A Search for Embryonic Antigens in Regenerating Intestine of the Adult Leopard Frog, Rana pipiens

Separate antisera were raised against blastula, gastrula, and neurula stage frog embryos. After absorption with adult liver, kidney, brain, intestine and oviduct, antisera generally showed precipitin