Cimetidine: interaction with oral anticoagulants in man

In 6 patients anticoagulated with warfarin, nicoumalone, or phenindione the addition of cimetidine prolonged the prothrombin-time (PT) by a mean of 12.6 s (range 5--23 s). In 7 volunteers taking daily subtherapeutic doses of warfarin the addition of cimetidine increased the PT from 19.4 to 22.9 s and the plasma-warfarin concentration from 0.96 to 1.76 microgram/ml. Cimetidine reduced the single-dose clearance of warfarin and antipyrine. The basis of the interaction between cimetidine and oral anticoagulants is probably inhibition of drug metabolism. Care should be exercised in concomitant therapy.

Single-photon counting system for measuring laser parameters

A single-photon counting system has been developed for measuring gas laser parameters. A linear accelerator provides nanosecond-wide pulses of heavy charged particles which are injected into a specially designed cell. The charged particles excite gas mixtures, and the temporal response of the emitted radiation is observed as a function of wavelength. The resulting data is analyzed to obtain pertinent parameters such as excited-state lifetimes, reaction rate constants, and quenching rate constants. At the present time nuclear pumper laser candidate gases are being examined.

The fixed horizontal neutron therapy beam at Edinburgh: dosimetry and radiation protection

A compact cyclotron producing 15 MeV deuterons has been installed at the Western General Hospital, Edinburgh, to extend the Medical Research Council's clinical trials of fast neutrons. Two treatment rooms are available one of which has an isocentric unit and the other a fixed horizontal beam which is the subject of this paper. A radiation protection survey has demonstrated safe levels of radiation throughout the building although there is some activation of the fixed horizontal beam cone resulting in doses to radiographers of 10 mrem per week. The calibration of neutron dose is discussed and the measurements of dose distribution described. Isodose and depth-dose data for both the neutron and photon components of the field are presented.

Enhancement of radiation killing of cultured mammalian cells by cordycepin

Asynchronous populations of rat hepatoma cells (H4) in log-phase growth survived a 3-hour exposure to cordycepin (3'-deoxyadenosine), and RNA antimetabolite, in a simple exponential fashion with a 'DO' of 43.8 microM/l. When cordycepin-treated cells were exposed to X-irradiation, the resultant survival levels were much lower than one would expect were the agents simply additive. Patterns of X-ray survival of cells treated with cordycepin were dependent on drug concentration, the predominant effect being to decrease the DO of the X-ray survival curve. The increased sensitivity of cells exposed to cordycepin to subsequent X-ray treatment persists for longer than 4 hours after drug administration. Although immediate cordycepin post-treatment of X-irradiated cells is less effective than pre-treatment, the interaction is still significant. Cordycepin treatment did not appear to reduce split-dose recovery or to inhibit the rejoining of single-strand breaks as measured by DNA sedimentation in alkaline-sucrose gradients.

Simultaneous bilateral parotid and submandibular gland calculi

A recent review of the medical literature revealed no recorded cases of simultaneous bilateral parotid and submandibular calculi. We present such a case with roentgenographic documentation.

Isolation of trimethyl amine oxide and other bases from the hydroid Tubularia larynx

1. Trimethyl amine oxide, dimethyl amine and choline chloride have been isolated from the marine hydroid Tubularia larynx and identified using physical constants and spectral data. 2. The presence of two guanidine molecules has been demonstrated.

Relative responses of an X-ray-resistant hybrid cell-line and its parent line to X-irradiation, ultraviolet light, actinomycin D and cordycepin

Using colony formation as an assay, a rat-mouse hybrid cell-line (HD1) and one of its parent lines (H4) have been studied as to their abilities to survive exposure to ionizing radiation, ultraviolet light, and the drugs actinomycin D and cordycepin. HD1 cells are more resistant than H4 to ionizing radiation, actinomycin D and cordycepin. Both cell lines respond similarly to ultraviolet light. When both cell-lines were co-treated with actinomycin D or cordycepin, the toxic effect of ionizing radiation was enhanced, whereas that of ultraviolet light (U.V.L.) was unchanged. The data suggest that RNA synthesis is more important immediately after irradiation with X-rays than with U.V.L. and that cells resistant to the toxic effect of ionizing radiation are also resistant to the toxicity induced by inhibitors of RNA synthesis.

Survival of synchronized V79 cells treated with X-rays and cordycepin

The survival of V79 Chinese hamster lung cells exposed to X-irradiation is reduced by co-treatment with cordycepin (3'-deoxyadenosine). This reduction is manifested principally by a decrease in the D0 of the X-ray survival curve from 199 rad in untreated cells to 106 rad in cordycepin-treated cells. Reduced survival is seen throughout the life-cycle when synchronized cell populations are exposed to both agents with cells in mid-S being especially sensitive.