Slow Growth Phase Research Articles

The development of “spontaneous” neoplastic transformation in vitro of cells from young and old mice

Thirty-six cell lines were established from various organs of embryo ( 18 days), young ( 3–20 days) and old ( 28–34 months) C 3H and C 57BL(a t) Icrf mice. Six of 14 lines from young mice and 10 of 21 lines from old mice produced tumours on subcutaneous inoculation into syngeneic mice after 190–638 days in culture ( 3–58 transfer generations). Neoplastic transformation did not seem to be related to the length of the slow growth phase before rapid in vitro growth began, final growth rate, method of initiation or transfer of cultures, extensive cell contacts, or age or strain of the donor tissue.

Effects of Ethylene and 2-Chloroethylphosphonic Acid on the Ripening of Grapes

The effects of ethylene gas, 2-chloroethylphosphonic acid, and the auxin, benzothiazole-2-oxyacetic acid, on the ripening of grapes (Vitis vinifera L.) was investigated. Ethylene hastened the start of ripening of Doradillo grapes when it was aplied for 10 days starting midway through the slow growth phase. 2-Chloroethylphosphonic acid applied to Shiraz grapes showed the same effect, but when it was applied earlier, during the second half of the first rapid growth phase or at the start of the slow growth phase of berry development, it delayed ripening. 2-Chloroethylphosphonic acid and benzothiazole-2-oxyacetic acid delayed the ripening of Doradillo grapes, and ethylene partially reversed the effect of benzothiazole-2-oxyacetic acid. The results demonstrate the importance of the slow growth stage in grape berry development and suggest that an auxin-ethylene relationship may be involved in the regulation of grape ripening.

Cytological changes in the developing ovary of the house fly fed milk and other diets

In the house fly, oogenesis from stages 1 to 4 occupied the last 2 days of the pupal period. The completion of the first ovarian cycle from stages 4 to 14. in the well-fed female at 25 °C, required between [Formula: see text] and 4 days. Growth of the follicle approached a constant exponential rate from stages 1 to 10. The period of vitellogenesis was divided into two phases: an early phase from stages 8 to 10, and a late phase of slower growth from stages 11 to 12 after the vitelline membrane was formed. Reproduction in the adequately fed female showed ovarian synchrony, all oocytes of a cycle developing at the same rate. In females fed only sugar water, oogenesis was arrested at stages 7 to 8, the potential resting phase. After oviposition, subsequent cycles from stages 7 or 8 were completed in about 2 days. As long as a mature egg was retained in the ovariole, the follicle of the next cycle remained at stage 8. The dynamics of the growing oocyte was related to changes in the nurse cells and follicular cells. The nature of the yolk spheres at different stages of development and the formation of the egg membranes was investigated.

Growth and senescence of the grape berry*

Benzothiazole-2-oxyacetic acid (BTOA) was applied to bunches of grapes (Vitis vinifera cv. Shiraz) at different times during their development and its effect on their subsequent growth was followed by measuring changes in berry weight, reducing sugars, malate, and tartrate. It lengthened the slow growth phase of berry development and this delayed ripening. It had no effect on the course of the first or second rapid growth stages. Greatest response to a single application was obtained when BTOA was applied at the end of the first growth stage or during the first week of the lag phase. Two and three applications made at 2-weekly intervals lengthened the lag phase more than a single application. During the prolonged lag phase malate continued to increase and reached a higher maximum than in untreated grapes. No consistent effect of BTOA on the tartrate content of grapes was apparent. The response of grapes to treatment with BTOA and other auxins is discussed in relation to growth and senescence of the grape berry. * This work was initiated at the Australian Wine Research Institute, Glen Osmond, S.A. 5064, Australia.

Experiments relating to the biosynthesis of bacilysin.

1. Bacilysin, a peptide which yields l-alanine and l-tyrosine on acid hydrolysis, was produced by a strain of Bacillus subtilis (A 14) in a chemically defined medium containing glucose, ammonium acetate or ammonium chloride, potassium phosphate and other inorganic salts, and ferric citrate. 2. Under the conditions used growth was diphasic. Bacilysin was formed during the second phase of slower growth, and there was little production during the stationary phase. Nevertheless, bacilysin production occurred when protein synthesis was inhibited by chloramphenicol. It thus appears that there is no obligatory coupling of protein synthesis and bacilysin synthesis. 3. When dl-[1-(14)C]alanine was added to a growing culture of B. subtilis, (14)C was incorporated into bacilysin, which contains an N-terminal alanine residue. 4. Under similar conditions virtually no (14)C was incorporated into bacilysin from dl-[2-(14)C]tyrosine, l-[U-(14)C]tyrosine or [1-(14)C]acetate, although these compounds were used by the cell for the biosynthesis of other substances. These results indicate that neither tyrosine nor acetate is a precursor of the fragment of bacilysin which yields tyrosine on hydrolysis with hot 6n-hydrochloric acid. 5. The tyrosine-yielding fragment of bacilysin was labelled with (14)C from [1,6-ring-(14)C(2)]shikimic acid. The biosynthesis of bacilysin thus appears to involve a diversion from the pathway leading to aromatic amino acids at the shikimic acid stage, or a subsequent one.

Slow exponential growth of Escherichia coli in presence of p-fluorophenylalanine. Effect of the analog on aromatic biosynthesis

1. 1. A new growth phase of Escherichia coli B in the presence of p-fluorophenylalanine is described. This is a slow exponential growth phase which follows the linear growth induced by the analog, and which continues for several generations until supplanted by a resistant mutant. A graphic analysis of the complete growth cycle is given. 2. 2. The p-fluorophenylalanine is incorporated exponentially during the slow exponential growth, without alteration, as a partial substitute for phenylalanine. 3. 3. Extensive filamentation of the organisms occurs during linear growth. Cell division is resumed in the slow exponential phase. 4. 4. The phenomena of inhibition of mass increase and inhibition of cell division are shown to be separable. Cell-division inhibition appears dependent on tyrosine deprivation or interference with tyrosine metabolism. It is postulated that dl -p- fluorophenylalanine interferes with aromatic biosynthesis by inhibiting enzymes early in the pathway and by partially repressing the synthesis of these enzymes. 5. 5. A new interpretation is made of the nature of the resistant mutant.

Transmission of colicinogeny between strains of Salmonella typhimurium grown together.

SUMMARY: Ability to produce colicines I, E1, E2, K or B was transferred to Salmonella typhimurium strain LT2 by growth in broth with suitable colicinogenic strains of Escherichia coli or Shigella sonnei. When LT2 (colI), i.e. carrying the colicine I factor, or LT2 (colB) were grown overnight in broth with LT2 col - (non-colicinogenic), c. 50 % of the latter became colicinogenic; LT2 (colE2) and LT2 (colK) did not transmit; LT2 (colE1) transmitted to only c. 0.1 % of the acceptor population. But LT2 carrying either colI or colB in addition to colE2, colK or colE1, transmitted both factors. When overnight broth cultures of LT2 (colI) and LT2 col - were mixed and incubated c. 40 % of the latter acquired colI by 20 hr. (when the viable count had doubled); but only c. 0.02 % acquired colI in 3 hr. The low initial transfer results from the fact that in a stock culture of LT2 (colI) only c. 1/5000 bacteria are ‘competent donors’, able to transmit colI. The later large increase in the proportion of colicinogenic bacteria probably results from ‘epidemic spread’ of the colI factor amongst the acceptor population, initiated by the few acceptor bacteria which originally receive it. It is supposed that most bacteria which have just acquired colI become competent donors. In a doubly colicinogenic strain most competent donors transmit both colicine factors. Aeration by shaking during incubation interfered with transmission of colicinogeny, probably by abolishing the prolonged phase of slow growth of unaerated cultures. Growth in the presence of acriflavine did not ‘cure’ LT2 (colI) or LT2 (colI) (colE2) of colicinogeny, nor of ability to transmit. LT2 (colE1) and LT2 (colE2) supported the epidemic spread of colI or colB about as well as did LT2 col -; but in LT2 (colK) the spread of colI was greatly reduced and that of colB somewhat reduced. The prior presence in an acceptor strain of one of the readily transmissible factors, colI or colB, did not interfere with the epidemic spread of the other. But LT2 (colI) did not become a competent donor on accepting colE2 and, by inference, colI from LT2 (colI) (colE2).

Growth of the Dandelion Scape

The growth of the flowering stalk of dandelion, Taraxacum officimele, is of considerable interest because of the presence of two distinct periods of rapid growth. The last of these precedes and accompanies the maturation of the fruit, and represents a resumption of rapid growth in what would normally be considered a mature organ. Miyake (8, 9) showed that growth of the dandelion scape may be divided into three phases : the first a fairly rapid, uniform growth, the second a phase of slow growth ; and the third, a rapid growth in the upper portions of the organ. Schmalfusz (10) showed that mitotic figures were present in elongating scapes up to the stage of shedding ripe fruits and were especially frequent preceding the periods of greatest scape elongation. As a part of a general study of the mechanism of cell elongation the experiments of Miyake and Schmalfusz have been repeated and extended. The data presented were obtained from extensive studies of the regions and periods of cell division and elongation in the dandelion scape, together with studies of cell volume, green and dry weight, and nitrogen content on a per cell basis.