Synthesis and induction of tyrosine aminotransferase in synchronized hepatoma cells in culture

The generation cycle of an established line of rat hepatoma cells (HTC cells) was studied using synchronized cell techniques. Dexamethasone phosphate (Dex), a synthetic adrenal corticosteriod which induces tyrosine aminotransferase (TAT) in HTC cells randomly distributed in the cell generation cycle, did not affect the durations of the various phases of the cycle. The activities of TAT and several dehydrogenases, and the rates of general protein and RNA synthesis, were studied throughout the cycle.Dex, at 10(-5)M, when added to a synchronized cell population in the latter two thirds of G1 phase or anywhere in the S phase, induces TAT. During the period made up of G2, M, and early G1, Dex does not induce TAT. However, radioisotope incorporation into specifically immunoprecipitated TAT continues during mitosis, when general protein and RNA synthesis are decreased.

Changes in Rate of Leakage of Potassium from Excised Disks of Apple Fruits Held at 20'c After Harvest

As early as 1928, Blackman and Parija suggested that the climacteric rise in respiration which is associated with ripening in most fruits might be due to changes in cell permeability. This view has been supported by recent observations on some tropical and subtropical fruits, viz. the avocado (Sacher 1962; Ben-Yehoshua 1964; Young and Biale 1967), the banana (Baur and Workman 1964; Sacher 1962, 1966), and the nutmeg melon (Von Abrams and Pratt 1967).

Comparisons between Granny Smith apples from healthy and green crinkle virus infected trees

Fruits harvested from Granny Smith trees known to be affected to varying degrees by apple green crinkle virus were held in cool store for five months before analysis for their total nitrogen and protein nitrogen contents. Fruit seed number, cell number, and dry matter content were also determined. There tended to be a greater incidence of superficial scald in fruit from infected trees. Fruits from infected trees were smaller, had a higher dry matter content, a greater proportion of protein nitrogen to total nitrogen, and fewer cells than those picked from healthy trees. Within infected trees the total nitrogen content decreased as the severity of fruit crinkling increased. The results are discussed in relation to effects of the virus on yield, the physiological status of infected trees, and a consideration of the likely storage disorders to be encountered in fruit from healthy and infected trees.