Abstract Phleomycin, a copper containing protein, has a broad range of antibiotics (3,4,6) anti tumor (7,9), and anti-viral (5) activity. At low concentrations it induces DNA breakdown and death in growing culture is of E. coli B, but has little effect on stationary phase bacteria (10) . However, its action can be strongly potentiated on stationary phase cells by the addition of certain compounds. This phenomenon is termed amplification.The mechanism of amplification phleomycin is not well understood. In this study the effects of various purine and pyrimidine analogues reported as amplifiers of phleomycin (2) were investigated on several aspects of nucleotide metabolism.

Thesis (Ph.D.)--University of Oklahoma, 1986. / Bibliography: leaves 201-206.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 88-102). Also available in electronic version.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 159-203).

Thesis (Ph. D.)--University of Wisconsin, 1965. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 200-217).

The de novo pathway of purine nucleotide biosynthesis in rat intestinal mucosa has been studied using respiring whole cell tissue suspensions and cell-free extracts prepared in isotonic sucrose or buffered saline. The antibiotic azaserine (O-diazoacetyl L-serine) was found to exert an inhibitory effect on the in vitro incorporation of formate-C¹⁴ into the acid-soluble and nucleic acid purines of intact cells when injected intraperitoneally into rats one hour before the animals were sacrificed. Such an inhibition could not be demonstrated if azaserine and a labelled precursor were added to incubation vessels simultaneously with tissue suspensions prepared from normal animals. This indicated that azaserine had to be in contact with a tissue constituent for a period of time before the enzymes concerned were affected. Studies with cell-free extracts of mucosal tissue showed that glycine-l-C¹⁴ could be metabolized in small amounts to a form which displayed some of the properties of glycinamide ribotide, a known intermediate in the de novo synthesis of inosinic acid by pigeon liver enzymes. Because azaserine does affect de novo synthesis of purines and because isotopic glycine is transformed to a form having properties in common with those reported for glycinamide ribotide, it appears possible that the enzymatic steps of purine synthesis in mucosal tissue are similar to those already known for pigeon liver. The level of free glycine in mucosal tissue has been measured by a method not previously employed. The results obtained are intermediate in value to those of the two groups who have studied the problem independently. An average value of 0.425 mg. free glycine per gram (fresh weight) of mucosal tissue was obtained. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Purine biosynthesis has been studied in vitro using surviving, whole cell suspensions of the mucosa from the small intestine of the rat. The preparation and use of such suspensions have been described as have been certain features of their metabolic behaviour. The techniques used to isolate and measure the radioactivity of the several purine fractions of mucosal suspensions containing 150-200 mg. of fresh tissue have been outlined. The de novo synthesis of purines by this tissue system was demonstrated by measuring the incorporation of several C¹⁴-labelled purine precursors into adenine and guanine of the acid-soluble (AS) nucleotides and the nucleic acids. Essential parts of this demonstration consisted of establishing the radiochemical purity of the isolated, purines, and of showing that the isotope incorporation was not attributable to bacteria present in the tissue suspension. Upon incubation of mucosal suspensions with formate-C¹⁴, adenine and guanine of the AS nucleotides displayed a rapid renewal, being approximately 40 and 14 times as radioactive, respectively, as the adenine and guanine of the mixed nucleic acids. The specific activity of AS adenine was approximately 6 times greater than that of AS guanine, and nucleic acid (NA) adenine was 2-3 times as active as NA guanine. Following incubation of the mucosal preparation, the suspending medium contained adenine, guanine and uric acid, but since these purines were only slightly radioactive they were regarded as breakdown products. Incorporation of formate-C¹⁴ by exchange reactions (as opposed to de novo synthesis) appeared to be excluded as a major process by the demonstration that two other purine precursors, glycine-1-C¹⁴ and bicarbonate-C¹⁴, also became incorporated into the purines. The theoretical incorporation of 2 molecules of formate for each glycine molecule used in the process of de novo purine synthesis was approached in these experiments by the observed incorporation of 2 - 4 molecules of formate per molecule of glycine. This is sufficiently close to the theoretical value to exclude a major incorporation by known exchange reactions. Time studies indicated that the renewal of AS adenine and guanine proceeded at an approximately constant rate with a decline in rate starting at 3 - 4 hours of incubation. In several experiments an initial lag in the rate of synthesis of NA purines was apparent. The rate of purine synthesis as measured by the incorporation of formate-C¹⁴ was not significantly affected by the addition of non-isotopic glycine or glutamine to the incubation medium. Similarly, glycinamide and 4-amino-5-imidazolecarboxamidine, both of which resemble known intermediates in purine biosynthesis, did not alter the incorporation of formate-C¹⁴ into the purines. Renewal of either AS or NA purines from formate-C¹⁴ did not take place in homogenates of intestinal mucosa. The incorporation of formate-C¹⁴ by the purines of the intestinal mucosa of the intact rat was measured 24 hours after administration of the isotope. In contrast to the in vitro experiments, the large differences between the specific activities of the acid-soluble and NA purines were absent in the intact animal, the levelling effect very probably being due to the 24 hour interval. A comparison of purine synthesis in the intact animal with that of the in vitro system suggested that guanine synthesis was suppressed in the latter. The use of intestinal mucosa for in vitro studies of purine metabolism has not hitherto been reported. In view of the demonstrated rapid synthesis of soluble purine nucleotides in this system, particularly of adenine nucleotides, it is felt that suspensions of mucosa may have useful applications in in vitro studies of purine biosynthesis. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Thesis (Ph. D.)--Ohio State University, 2004. / Document formatted into pages; contains 171 p. Includes bibliographical references. Abstract available online via OhioLINK's ETD Center; full text release delayed at author's request until 2005 Nov. 10.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 18, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Rainer Glaser, Thesis Supervisor. Includes bibliographical references.

An investigation was made of the effects of the purine analogs, 8-azaguanine, 8-azaxanthine, and 6-mercaptopurine, and the purines adenine and guanine, on cell growth, mitosis, and desoxyribonucleic acid (DNA) synthesis in primary roots of Vicia faba seedlings grown in aerated solutions. Root elongation was used as a measure of cell elongation; mitotic frequency was determined in free cell suspensions prepared from 1 mm-long root tips; the relative content of DNA was determined microspectrophotometrically by the two-wavelength method. It was shown that the balance between root elongation and mitosis in the root tip could be influenced by the amount of aeration and by adenine. Increased aeration stimulated root elongation and depressed mitotic frequency; adenine stimulated mitosis, inhibiting, at the same time, root elongation. 8-azaguanine, in concentrations of 10 p.p.m. and higher, stopped mitosis within 24 hours and greatly reduced root elongation and the fresh and dry weights of roots within 72 hours. This inhibitory effect on both root elongation and mitosis was positively correlated with aeration. 8-azaguanine in a concentration of 1 p.p.m. significantly reduced mitotic frequency but slightly stimulated root elongation. The inhibition of root elongation could be best, though incompletely, reversed by 40 p.p.m. adenine or guanine. The mitotic inhibition could be partially reversed by 40 p.p.m. guanine; adenine, at a concentration of 80 p.p.m., not only completely relieved mitotic inhibition, but increased the mitotic frequency to a level higher than that of the water controls. Concentrations of 6-mercaptopurine and 8-azaxanthine comparable with those of 8-azaguanine had no inhibitory effects. Roots treated with 20 p.p.m. 8-azaguanine for 24 hours and then transferred into 80 p.p.m. adenine showed a higher mitotic frequency than the control within 24 hours after transfer. Roots transferred from 8-azaguanine into water showed some mitosis 48 hours after transfer; in this case mitosis was restricted to the partially differentiated and elongated cells of the provascular bundles. DNA content of interphase nuclei in the controls showed this distribution: a sharp 2C peak (about 65 per cent nuclei), a much lower 4C peak (about 20 per cent nuclei), and intermediates (about fifteen per cent). There were no polyploid nuclei in the apical meristem of the root. The DNA content of chromosomal groups in different mitotic stages demonstrated the accuracy of the two-wavelength method which was used. The DNA content of nuclei in roots treated with 20 p.p.m. 8-azaguanine was distributed in a 2C peak (about 80 per cent nuclei) and a 4C peak (about 20 per cent nuclei). There were no intermediates in treated roots and no nuclei contained a higher amount of DNA than 4C. The percentage of 4C nuclei did not increase with time. From the evidence that the mitotic inhibition induced by 8-azaguanine could be completely reversed within 24 hours by subsequent treatment with adenine, and from the findings concerning the distribution of DNA in inhibited nuclei, it may be concluded that 8-azaguanine was not incorporated into DNA. The possibility that 8-azaguanine exerts its inhibitory effects through interference with ATP metabolism is discussed. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate