Enhanced Survival Time Research Articles

Do anticonvulsant drugs exert protective effect against hypoxia?

The effect of anticonvulsants was studied on survival time in mice subjected to hypoxia either by decompression or by prolonged asphyxia. Except trimethadione all the compounds tested enhanced survival time. These results suggest that the protective effect observed might be due directly to the inhibition of hypoxic convulsive seizures.

Effects of constant illumination and hyperoxia on thermal tolerance of goldfish

1. 1. Survival times at upper lethal temperatures for goldfish acclimated at 5, 10, 20, 22, 30 and 35°C were enhanced among those in hyperoxia during exposure to the lethal temperature and those which had received 11–17 days constant prior illumination as compared to controls not receiving such treatments. 2. 2. Constant prior illumination when combined with hyperoxia during exposure to a lethal temperature enhanced survival time much more than either treatment separately. 3. 3. All enhancements of survival time were greatest in the 20–30°C range for acclimation temperatures. 4. 4. There are some indications that at 35°C acclimation temperature stress effects militate against the manifestation of the above enhancement.

A Chemically Defined Medium for Maintenance of Schistosoma mansoni

A completely synthetic medium containing amino acids, nucleic acid derivatives, vitamins, salts, and glucose for the maintenance of schistosomes in vitro is herein described. This medium appears adequate for short-term survival of these parasites, since they can be kept alive for periods somewhat more than a month. During early in vitro maintenance, the worms lay eggs and otherwise demonstrate normal behavior patterns. However, after about 20 days they begin to deteriorate, indicating that this artificial medium is far from optimal. The fundamental importance of determining the nutritional requirements of parasites hardly needs to be emphasized. Although the classical treatments of fluke infestation have depended on the administration of poisonous heavy metals, it seems reasonable to suggest that such methods should be supplanted by more reliable and less toxic procedures. A beginning step towards a more rational approach to the therapy of schistosomiasis might be the determination of the essential amino acids required by this parasite. Until recent years most of the in vitro maintenance fluids for schistosomes have been composed of a balanced salt solution to which various mammalian sera and/or embryonic extracts, amniotic fluids, or ascitic fluids were added (Lee and Chu, 1935; Hoeppli, Feng and Chu, 1938; Newsome and Robinson, 1954; Senft and Weller, 1956). Such fluids allowed prolonged survival of the worms and, in some cases, growth and regeneration of young adults. Limited egg production in vitro, using a variety of diluted sera (Cheever and Weller, 1958; Robinson, 1960) has also been reported. However, these successes have not adequately advanced our understanding of the nutritional requirements of Bilharzia. Although many of the above media can be reproducibly prepared, their components are variable, and either unidentified or vaguely defined. Few investigators have employed chemically defined media for the in vitro studies, a notable exception being Ross and Bueding (1950), who found survival of S. mansoni limited to 18 hours in a holidic medium. The addition of Received for publication 9 February 1961. This work was supported by the National Institutes of Health, Grant No. E-1689(C-3). muscle extract derivatives (largely unidentified substances called protogens) enhanced survival time considerably. Mao et al. (1957) found that S. japonicum would survive about 6 days in a Tyrode-Glucose-Vitamin mixture. Such short-term survivals are, however, quite inadequate for growth, regeneration, or egg production studies. The apparent ease with which certain strains of mouse fibroblasts can be maintained in a protein-free chemically defined medium (Evans et al., 1956), encouraged a trial of such a solution in schistosome work. It seemed logical that a synthetic medium modeled on previous chemical analyses of chick embryo extract (Westfall, Peppers, Sanford, and Earle, 1954) and horse serum (Westfall, Peppers, and Earle, 1954) might be tolerable for schistosomes, especially since schistosomes can be grown to maturity in laboratory mice. This paper will record moderate success in both survival and egg-production in such a completely synthetic medium. MATERIALS AND METHODS