Cloning of rat kangaroo (PTK2) cells following laser microirradiation of selected mitotic chromosomes

Mitotic chromosomes of rat kangaroo cells were irradiated with a green argon laser microbeam without prior dye sensitization. Deoxyribonucleic acid-negative chromosome paling was observed. The irradiated cells were isolated and cloned into viable populations.

Chromosome lesions produced with an argon laser microbeam without dye sensitization

Improvements in the argon laser microbeam have made it possible to cause damage to chromosomes of tissue culture cells without prior treatment of the cells with a photosensitizing agent. These results have been confirmed independently in two laboratories.

Enzyme inactivation with ultraviolet laser energy (2650 Angstroms)

Inactivation of rat heart lactate dehydrogenase was accomplished by irradiation of the enzyme in solution with a frequency quadrupled neodymium glass laser.

Regulation of segment-building during the postembryonic development of a common milliped

Starvation of larvae of the milliped Narceus annularis results in the formation of a smaller than normal number of body segments in the early stadia. However, this reduced number is compensated for by subsequent formation of a larger than normal number of body segments in the later stadia, or by the addition of extra segment-building stadia. Apparently there is a mechanism whereby the milliped "keeps count" of the number of body segments produced and can regulate the production of these segments from a proliferative region so that the total number of body segments at sexual maturity is within the normal range for the species.