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In the first-known application of its kind, shockwave lithotripsy and contact-solvent dissolution of large, calcified gallstone burdens were performed simultaneously with three chemical solvents, each tested separately in an in vitro model, with the combined effects on gallstone eradication examined. Two solvents, ethyl propionate and isopropyl acetate, were chosen for their solubilizing ability and potentially high level of patient safety. The third solvent, a 70%:30% mixture of methyl tert-butyl ether (MTBE) and dimethyl sulfoxide (DMSO), was chosen for its known ability to accelerate the dissolution of calcium-containing gallstones. All stones were matched for size, weight, and number. Gallstone lithotripsy performed in ethyl propionate was significantly more effective (P less than .02) in the production of fragments less than 2 mm when compared with bile; lithotripsy with isopropyl acetate and the MTBE/DMSO mixture showed no statistically significant effect. Biliary lithotripsy performed in an ethyl propionate medium may enhance gallstone dissolution and the production of small fragments (diameter less than 2 mm).

Purpose To determine what interaction and effect different cholesterol gallstone solvents have on catheters used for gallstone chemolysis. Materials and Methods Five types of catheters used for biliary procedures were chosen: polyethylene, Percuflex, silicone, Silitek, and polyurethane. The solvents chosen were methyl tert -butyl ether, ethyl propionate, isopropyl acetate, and N-propyl acetate. After incubation of the catheters in the solvents for 72 hours, they were air dried. Weight and area changes were determined for each catheter. Additionally, carbon-13 nuclear magnetic resonance (NMR) spectroscopy was performed for analysis of composition changes. Results Three catheters – silicone, Silitek, and polyurethane – showed changes in their physical characteristics that would make them less desirable for stone chemolysis. The silicone catheter showed changes in elastic texture as well as a marked weight reduction. The Silitek and polyurethane catheters had similar, but less dramatic changes. C-13 NMR analysis of collected solvents showed that commonly used plasticizers were leached out of some catheters. Conclusion These results suggest that all catheters are not suitable for use with all solvents. The choice of catheter should be made based on the solvent in use. The polyethylene catheter performed best under the conditions and endpoints used in this study.

The rejoining of radiation-induced DNA breaks, characterized by 5′ termini, was measured by the polynucleotide kinase method. This method has potential clinical value because DNA damage can be measured for cells within solid tissue. Following irradiation of a human squamous-cell carcinoma, DNA rejoining occurred, but at a slower rate than observed for mammalian cells in culture. The results of the study indicate that cells within solid tumors, in situ, are able to repair at least some radiation-induced DNA damage. The importance of this type of repair to tumor response following therapeutic radiology is not known at present.

The influence of thymine starvation on the single-strand molecular weight of deoxyribonucleic acid (DNA) from Escherichia coli was determined by sedimentation through gradients of alkaline sucrose. Growth of cells for as long as 150 min in thymineless medium did not significantly reduce the molecular weight below the control value of 2.4 ± 0.3 × 10 8 daltons. Incubation of cells in thymineless medium after exposure to 500 ergs/mm 2 of ultraviolet light or 20 krad of 137 Cs gamma rays did not appear to block the rejoining of single-strand breaks associated with irradiation. Thus, DNA repair enzymes, presumably including DNA ligase, are not significantly inhibited by thymine starvation.

L cells irradiated while in growth medium or in a balanced salts solution showed a rapid appearance of DNA breaks characterized by 5′ phosphoryl termini. Following irradiation, the number of breaks quickly reached a maximum, after which they were rapidly repaired. Dinitrophenol, an inhibitor of aerobic oxidative phosphorylation, prevented the DNA breaks from appearing.

The repair of radiation induced DNA damage in some micro-organisms has been explained on the basis of the “cut-and-patch” hypothesis. This hypothesis postulates that radiation produces alteration of the DNA bond structure, nucleolytic enzymes convert the bond alterations into frank breaks, and then the breaks are repaired by an enzyme ( s ) which has properties similar to DNA polymerase. In this paper we give experimental and theoretical evidence to support the notion that the “cut-and-patch” mechanism very likely is responsible for the repair of radiation induced DNA damage in cultured mammalian cells.

Intracellular adenosine triphosphate (ATP) levels were measured in both hypoxic and aerobic cultures of V79 Chinese hamster cells treated with 5-thio-D-glucose (5-SH-D-Glc). This glucose analog, a known inhibitor of D-glucose transport and metabolism, reduced ATP in cell cultures allowed to become hypoxic by cell metabolism, but not in aerobic cultures treated similarly. Cells depleted of ATP were unable to rejoin x-ray-induced deoxyribonucleic acid (DNA) strand breaks as measured by the alkaline surcrose gradient sedimentation technique. Results show that 5-SH-D-Glc leads to reduced energy metabolism in cells dependent on glycolysis for ATP production. The inference for radiation therapy is that inhibition glucose metabolism selectively depletes energy reserves in hypoxic cells, rendering these cells more radiosensitive and leading to a more effective tumor treatment.

Ionizing radiation of oxygenated aqueous solution is known to produce superoxide as a secondary product of radiation,1–3 Part of the cellular injuries caused by radiation can be attributed to the acute increase of superoxide. Addition of Cu-Zn superoxide dismutase (Cu-Zn SOD) to the extracellular medium can significantly protect cultured cells against radiation damage.4 Adding Cu-Zn SOD to cultures of myoblasts protected them from a radiation-induced decrease in viability and altered morphology5 as well as chromosomal damage.6

The relative biologic effectiveness (RBE) of fast neutrons in the production of single strand DNA breaks is 1.6 as compared to that of 250 kVp x rays. Monolayers of L-929 cells were treated with dinitrophenol during irradiation to prevent the DNA strands from rejoining; the extent of DNA damage was measured by the alkaline sucrose sedimentation method. The RBE for DNA damage is essentially the same as the RBE measured by cell survival methods.

Copper(II)(3,5-diisopropylsalicylate)2 (Cu-DIPS), administered subcutaneously to mice at 80 mg/kg body weight, had marked radioprotective activity. Given 3 h before exposure to 8.0 Gy (800 rad) irradiation, Cu-DIPS increased the 42-day survival from 40% to 86%. Seven days after exposure to 8.0 Gy, there were severe reductions in spleen weight (73%) and cellularity (98%) in both Cu-DIPS- and vehicle-treated mice. Viable spleen cells collected 7 days after irradiation were totally unresponsive to mitogenic or antigenic stimulation regardless of Cu-DIPS or vehicle treatment, suggesting that Cu-DIPS did not prevent radiation-induced damage to mature lymphocytes. At 14 days, when Cu-DIPS-treated mice started to show improved survival over vehicle-treated mice, spleen weights and cellularity were 2.5- and 3.5-fold higher, respectively, in Cu-DIPS-treated mice. Treatment with Cu-DIPS not only enhanced splenic repopulation, but also accelerated the reappearance of both B and T cell reactivities. Spleen cell responsiveness to the B cell mitogen, lipopolysaccharide (LPS), and the T cell mitogen, concanavalin A (Con A), regenerated significantly faster in Cu-DIPS-treated mice. Cu-DIPS also significantly accelerated the regeneration of T-dependent antibody induction. Based on these assays of immunocompetence, Cu-DIPS-treated mice had, on average, a seven-fold greater capacity to respond to immune stimulation than vehicle-treated mice 24 days after irradiation.

Using the polynucleotide kinase method, we were able to demonstrate the repair of radiation induced DNA breaks in mouse liver DNA and in L cells. The specificity of the enzyme indicates the breaks to have 5′ phosphoryl termini.

In an earlier paper we attempted to show the “cut-and-patch” mechanism to be responsible for the repair of radiation induced DNA damage in cultured mammalian cells. The experimental basis was provided by survival studies. For the present investigation we used the polynucleotide kinase method to measure directly the appearance and rejoining of radiation induced DNA breaks characterized by 5′ PO 4 termini. A multicompartmental mathematical model was developed, and estimates of parameter values were made by experiments with L cells. The results suggest most of the frank DNA breaks following irradiation to be a consequence of endogenous nucleolytic processes and not due to the radiation, per se . Because of the massive cell killing which occurs in spite of preventing the appearance of DNA breaks, we postulate the existence of radiation induced DNA changes which (1) are not liable to endogenous nucleolytic processes and (2) cause cell lethality.

SummaryStarved L cells show a radiation-induced cyclic labeling of the acid-insoluble fraction when adenosine and deoxyadenosine are used as labeled precursors. The response consisted of a rapid uptake and loss of label. A similar effect has also been reported for 32P labeling of DNA.These findings support the idea that X-irradiation of mammalian cells produces increased action of an enzyme which rejoins single-strand breaks in DNA. The enzyme mechanism involves formation of a transient DNA-adenylate complex. In such a reaction, labeled adenylate should enter and then leave the DNA fraction. The results reported here agree with such a mechanism.

Experiments with bacteria suggest that extensive DNA degradation is an important step in the repair of radiation injury. Because of the potential importance, similar experiments with cultured mammalian cells were performed. L cells prelabeled with ${}^{3}{\rm HTdR}$ were suspended in medium and irradiated with doses of 0, 100, 500, and 1000 rads of 250 kVp x-rays. The results showed: (a) No massive DNA degradation occurred during the first 6 postirradiation hours; (b) although a small amount of radioactivity is released into the suspending medium, this is not increased by increasing dose of radiation; (c) the release of the radioactivity occurred in the presence of 2,4-dinitrophenol-an uncoupler of aerobic oxidative phosphorylation; (d) most of the released radioactivity was in the form of thymidine; and (d) the intracellular concentrations of alkaline deoxyribonuclease and DNA polymerase were not increased after irradiation.

The uncoupler of aerobic oxidative phosphorylation, 2,4-dinitrophenol (DNP), has been previously shown to decrease the radiation sensitivity of L cells. In the present investigation we performed paired irradiation experiments with DNP-treated cells. Although DNP treatment virtually stops macromolecular synthesis, the paired-dose survival curve showed a definite "repair" segment. The absolute survival reached by the DNP-treated cells was greater than that in parallel irradiated control cells kept in complete growth medium.

The uncoupler of oxidative phosphorylation, 2,4-dinitrophenol (DNP) has been shown to decrease the radiosensitivity of L cells in spite of producing a severe depression of DNA, RNA, protein, and ATP synthesis. To further explore these findings, experiments were performed with other compounds which affect oxidative phosphorylation. These included studies with asynchronous L cells and with L cells synchronized by the double thymidine block technique. The results showed that two uncouplers of oxidative phosphorylation, arsenate and DNP, produced an increase in postirradiation survival. Two inhibitors of oxidative phosphorylation, azide and cyanide, although depressing macromolecular synthesis, caused no increase in postirradiation survival. Cyanide, in fact, produced a slight decrease in survival. Experiments with synchronized cells indicate that the effects of arsenate are chiefly exerted on cells in S phase, while the effects of DNP are distributed throughout the intermitotic interval.

Mouse L cells show a cyclic32 P labeling of DNA following relatively low doses of x-rays. This effect appeared for cells which had been starved or treated with 2,4-dinitrophenol (DNP) but not for cells irradiated in growth medium. The response consisted of a rapid uptake and loss of label. Changes in ATP metabolism paralleled the cyclic labeling of DNA. This behavior possibly explains the enhanced repair of radiation injury previously described for DNP treated cells.