It was demonstrated previously that the median survival time (MST) of rats exposed to low temperature was decreased when cold challenge was immediately preceded by whole-body x-irradiation. To determine if the decreased tolerance of irradiated rats to cold was the result of radiation damage to specific sites, partial-body irradiation studies were conducted. Survival times at -17°C were determined for groups of juvenile male rats that were exposed to cold within 130 minutes after x-irradiation (1000 rad) of the head, body, hindquarters, or the whole body. The MST's of the head, body, and whole-body irradiated groups were similar, and were significantly less than that of the nonirradiated control group. No radiation-induced reduction in survival time in the cold was observed in the hindquarters-irradiated group, even though the irradiated mass was about twice that of the head group. After a radiation dose of 500 rad, cold tolerance was equally reduced by body or whole-body irradiation, but not affected when...
Two ATP-hydrolyzing enzyme systems (ATPases), possibly lipoprotein in nature have been isolated from particulate fractions of rat cerebral cortex homogenates. They consist of at least two components, one Mg++ dependent and the other Mg++, Na++ and K++ dependent. ATP hydrolysis is measured both by orthophosphate and hydrogen ion liberation and a lack of stoichiometry exists (H++ ion release two times orthophosphate formation) over the first 90 sec of the reaction. H++ ion and phosphate release are sensitive to strophanthin, but only in the presence of Na++ and K++. Sulfhydryl inhibitors including p-hydroxymercuribenzoate (POMB) and iodoacetate (IAA) inhibit both basic and Na+-K++-activated ATP hydrolysis, but the enzyme system is more resistant to N-ethylmaleimide (NEM), especially the initial “spurt” of H+ ion release. Certain gases have an action on enzyme activity, both to decrease (cyclopropane) or increase it (air, nitrogen) at pressures above one atmosphere.
: A step-by-step procedure is given for embedding L5178Y cells in fibrin gels so that individual cells may be observed repeatedly from their initial single state up to the formation of a colony. (The method is a modification and extension of the method of Schindler). An experimental example of the types of information obtainable is presented. (Author)
: The elimination of I 131-labeled horse serum albumin was used as a semi-quantitative measure for antibody production in mice. The parameters used for measuring the antibody production by means of the antigen elimination method were the induction period, the slope of the elimination curve and the T99 (time, in hours, required for the elimination of 99% of the amount of antigen present in the blood at time zero). It was found that the quantitative measurement of the immune elimination depended on the immunizing dose and on the tracer dose. The effects of various immunizing doses and of tracer doses on the observed immune response could be correlated in part with the amount of antigen present in the plasma at the onset of antibody formation. It was observed that only a fraction of the I 131-labeled alum-precipitated horse serum albumin injected was able to equilibrate in the intra- and extravascular spaces. The antigen in this 'albumin pool' was eliminated in a manner identical to intravenously injected I 131-horse serum albumin in non-immunized mice. The remaining portion of the antigen, presumably localized in various tissues, was eliminated at a much slower rate. It was postulated that the stored antigen was able to react with antibodies in the circulation, thus decreasing the amount of antibody available for elimination of labeled antigen. The possible implication of these findings for measurement of antibody formation under standard conditions is discussed. (Author)
The isolated rat liver perfusion system has been used to study the release of bile phospholipid P32 following the injection of inorganic P32 into the perfusate. It was demonsrtated that in the absence of added bile salt very little PLP32 was excreted into bile, but when bile salt was added to the perfusate the PLP32 excretion increased markedly. At the start of bile salt infusion, the specific activity of the bile phospholipids was lower than that of the liver, but at later times the specific activity of bile phospholipids was greater than liver PL specific activity. It is suggested that bile acids play an essential role in the transport of phospholipid from liver to bile.
: The kinetics of recovery of sheep in terms of time-dependent changes in radiosensitivity (LD50) have been evaluated as a function of dose rate and size of exposure to 60Co gamma or 1 Mvp X-rays. Although there were certain quantitative differences in recovery pattern, as related to both dose rate and size of the conditioning exposure, the basic pattern can be qualitatively described as consisting of three distinct phases. The first phase, lasting 5 - 10 days, consists of a 'shoulder' or very slow recovery. This is followed in the 15 - 20 day post-conditioning period by rapid recovery which proceeds to an 'overrecovery' or radioresistance of LD50's considerably greater than normal (controls). The resistance was only a transient phenomenon and during the 24 - 30 day period the animals had returned to a more sensitive condition with LD50's slightly less than normal. This third phase appeared to remain at least as long as 75 days and may represent either a very slow recovery or the irreparable fraction. Changes in the survival time of decedents in the challenge LD50 studies appeared related to the recovery period. The mean survival times were shorter in the 20 day experiments. Speculation is offered as to physiological changes that might account for such a relationship. (Author)
: Young adult male LAF1 mice were exposed to a single (300 R) dose of X rays, followed one day later by an intraperitoneal injection of urethan, 0.08 mg or 0.2 per gram body weight Cortisone acetate was injected subcutaneously, 7 injections of 2.5 mg each, on alternate days beginning one day after irradiation. The mice were sacrificed 25 to 26 weeks after the urethan injection, and the enumeration of lung tumor incidence was made by standard procedures. The percent of mice bearing lung tumors was highest (50%) in the group receiving 300 R plus urethan (0108 mg/g), as compared with 12.5% in the control mice irradiated only, and 16% in those receiving urethan only. Thus, X radiation and urethan can be additive for lung tumorigenesis. (Author)
: Experiments have been conducted to compare the time course of recovery for acute exposures in several species of animals. The object of these experiments is to define species differences in recovery potential, to seek the physiological basis for differences in recovery potential, and to provide both generalizations and meaningful estimates for recovery in humans subjected to acute (prompt) or protracted exposures. The purpose of this report is to review dose-rate studies with sheep and to describe recent preliminary experiments with swine. (Author)
: Intraperitoneal and intravenous injections of tracer quantities of 3H- or 14C-labeled deoxycytidine (CdR) were used to investigate the biologic half-life, the miscible pool size, and the turnover rate of CdR in normal and X-irradiated rats. The specific activity of highly purified CdR isolated from blood plasma samples taken at various times after injection of the tracer CdR was used as the basis for calculating these values. The mean values observed for normal rats were: biologic half-life 116 minutes, miscible pool 790 micro g/rat (100 to 180 g), and turnover rate 7.0 mg/24 hours/rat. The miscible pool of CdR appeared to be non-uniform, with the intracellular concentration appreciable higher than the general body-water concentration. About one-third of the total miscible CdR appeared to be intracellular. After relatively low doses of whole-body X-irradiation (25 to 100 rads), there were alterations in the turnover kinetics of CdR, but the presence of non-steady state made computation of the above three values impossible. However, the data are fully consistent with an increase in the miscible pool size of CdR, occurring as early as 1 hour postirradiation. The data do not provide information as to the mechanism for this apparent increase. (Author)
: The mechanisms for protection through parabiosis against both the acute intestinal and hematopoietic radiation death were investigated in two separate experiments. The length of time after irradiation that the parabiosis must remain intact for protection to occur was investigated in the first experiment. The data show that if surgical separation is delayed to 48 hours postexposure, protection against 3- to 5-day death occurs, and if delayed to 96 hours, protection against 30-day lethality also occurs. The second experiment was designed to test the quantity of whole-body radiation that one member of a parabiotic pair could receive (dose range 250-1000 R) and still provide protection to the simultaneously irradiated partner (1500 R). The results of this experiment show that over the dose range tested, none of the doses alters the animal's capacity to protect an irradiated partner (1500 R) against the 3- to 5-day death. Substantial 30-day survival also occurred with all the test doses employed except at the highest exposure level (1000 R). The findings are consistent with the hypothesis that protection through parabiosis against 3- to 5-day death is one of electrolyte and fluid maintenance and protection against 30-day mortality is through transfer in peripheral blood of stem cells capable of repopulation of bone marrow. (Author)
Abstract : The effects of brief alternating and square wave currents on gastric bioelectric activity and acid secretion were studied at frequencies between 10 and 10000 cycles/sec. Whereas acid secretion remains unchanged, potential and conductance are inversely affected by both wave forms, indicating a depolarization of the epithelium. Excitation conditions allowing optimal recovery from pulsing (100 cycles/sec and 10 V) are similar to those required to affect other preparations like squid axon and brain or muscle slices. Isolated mucosa requires less power for the same response as occurs in whole stomach. Electrical pulses apparently act directly on the mucosal membranes since neither atropine (0.001 M) nor TTX (1.6 x 000001 M) will block the depolarization effect. Unlike atropine, TTX still permits the standard response caused by 0.01 M Ach, namely inhibition of potential without conductance increase. (Author)
