Benjamin Mehlman

Cultural and physiological observations on Trypanosoma rhodesiense and Trypanosoma gambiense.

The cultivation of the trypanosomes of the brucei group is generally conceded to be much more difficult than that of the members of the lewisi group. While the latter have been cultivated in a variety of media and have been studied to some extent from the standpoint of their nutritional requirements and metabolic activities (Lwoff, 1940; von Brand, Johnson, and Rees, 1946; Chang, 1948), the cultivation of the former has been less successful, and therefore very little physiological information is available concerning them. Reichenow (1937b) stated that the addition of sugar did not improve his medium for the cultivation of the pathogenic trypanosomes. von Brand and Johnson (1947) found that the respiration of the proventricular form of T. gambiense was sensitive to cyanide. This is in contrast to that of its bloodstream form. Three types of media have given some measure of success in the cultivation of the pathogenic African trypanosomes. On blood agar media they grow either in the water of condensation (Novy and McNeal, 1904; Thomson and Sinton, 1912), or form colonies on the surface of the agar (Weinman, 1946). In liquid media (von Razgha, 1929; Reichenow, 1932, 1934; Brutsaert and Henrard, 1938) they aggregate commonly on the surface of the settled red cells. Slightly more viscous media were developed by Ponselle (1924) and Weinman (1944). They did not indicate where growth occurs in this type of medium. Most investigators use human blood as the blood of choice in the preparation of their media. Those who have used animal blood (Thomson and Sinton, 1912; Reichenow, 1932; Ponselle, 1924; Prates, 1928) did not present data which indicate whether such blood will sustain subcultivation for an indefinite period. In the first section of this paper we describe a diphasic blood agar medium which incorporates a number of features from the above media. It is less difficult to prepare than Weinman’s (1946) medium which it resembles in several respects. The remarkable intensity of sugar consumption by the bloodstream form of the pathogenic African trypanosomes (Yorke, Adams, and Murgatroyd, 1929; von Brand, 1933; Chen and Geiling, 1945; von Brand and Tobie, 1948) suggested the desirability of quantitative studies on sugar utilization by culturestages of these species. The data concerning this point, as well as data on the ammonia production, are summarized in the second section of this paper. 1. CULTURAL OBSERVATIONS Media employed

STUDIES ON THE ANAEROBIC METABOLISM AND THE AEROBIC CARBOHYDRATE CONSUMPTION OF SOME FRESH WATER SNAILS

1. Lymnaeidae and Physidae tolerated complete lack of oxygen less well than Planorbidae or operculates belonging to different families.2. All species consumed carbohydrate under anaerobic conditions and produced carbon dioxide and lactic acid. While in several species the lactic acid produced was sufficient to account for all or a large part of the carbon dioxide as liberated from bicarbonate, this was not the case in other species.3. The anaerobic metabolic level as measured by carbon dioxide production and carbohydrate consumption of the resistant species was, on an average, lower than that of the nonresistant ones. The former did not accumulate lactic acid within their tissues during an anaerobic period, while the latter did so to a marked degree.4. In most species the anaerobic carbohydrate consumption was only slightly higher than the aerobic rate. One of the reasons for this may be the probable occurrence of aerobic fermentations in these species.5. Lactic acid was quantitatively a major end product...

Observations on the metabolism of bacteria-free larvae of Trichinella spiralis

Abstract 1. 1. The larvae of Trichinella spiralis consume aerobically and anaerobically about the same amount of glycogen, while lipid consumption occurs only under aerobic conditions. 2. 2. The major endproducts of the carbohydrate fermentation are volatile fatty acids, especially valeric acid, while only traces of lactic acid are produced. Keto substances in small amounts are produced only in the presence of oxygen. Part of the acids is excreted as free acids, while another part may be excreted in the form of ammonium salts. 3. 3. Carbohydrate fermentation is the process which allows the larvae to survive anaerobic processes, but it is insufficient to allow motility. It is probable that a major part of the oxygen consumed is used for the oxidation of lipids and this process may be of importance for the motility of the larvae.

FURTHER STUDIES ON THE ANAEROBIC METABOLISM OF SOME FRESH WATER SNAILS

1. Fresh water snails exposed to anaerobic conditions produce volatile acids which are partly. excreted into the medium and partly accumulate in the tissues.2. The acids formed by Australorbis glasbratus and Helisoma duryi were identified by chromatographic means and crystallographic data as propionic and acetic acids.3. While bacterial formation of these acids cannot be excluded categorically, some evidence is adduced to the effect that they may be produced by the snail tissues.4. The evidence indicates that the species not resistant to anaerobiosis are killed primarily by the accumulation of lactic acid, while the resistant species are more tolerant to the lack of oxygen due to the fact that they accumulate in their tissues the less toxic fatty acids rather than lactic acid.5. Most of the carbon dioxide evolved by anaerobically kept snails is of direct inorganic origin.

The influence of lack of oxygen on Schistosoma mansoni cercariae and on infected Australorbis glabratus

Abstract Anaerobic studies were made both on the cercariae of Schistosoma mansoni and on Australorbis glabratus infected with that parasite. Although infected snails withstood 6 hours under anaerobic conditions most of them died when kept anaerobically for 16 hours, indicating that the presence of the infection makes them more susceptible to damage from lack of oxygen than uninfected snails. Shed of cercariae from infected snails was greatly reduced under anaerobic conditions and most freshly shed cercariae died rapidly when deprived of oxygen. Nevertheless, snails held anaerobically for 6, and even 16 hours shed normal cercariae when returned to an aerobic environment indicating that, although the free cercariae cannot survive without oxygen, those in the snail can. Cercariae shed by snails after they had been kept anaerobically for 4 hours were as infective for mice as were cercariae from normal snails. Five percent of oxygen in the environment permitted normal shed and survival of cercariae. On the other hand, at 0.7% oxygen the shed of cercariae was greatly reduced but freshly shed cercariae were not damaged. Infected snails stored less polysaccharide than uninfected ones. In anaerobic experiments, the molar ratio between polysaccharide consumed and carbon dioxide and volatile acids produced differed from that observed in uninfected snails. The anaerobic metabolic level of both infected and uninfected snails of the Dominican strain was higher than that of snails of the Puerto Rican strain.

RELATIONS BETWEEN PRE- AND POST-ANAEROBIC OXYGEN CONSUMPTION AND OXYGEN TENSION IN SOME FRESH WATER SNAILS

1. The respiration of four species of fresh water snails was somewhat dependent on the oxygen tension below 21 per cent oxygen with only minor differences among the various species.2. The degree of dependency was influenced little, if any, by alteration of the metabolic rate of Australorbis glabratus, but some changes were obtained in the cases of Helisoma duryi and Lymnaea stagnalis.3. All species showed a long lasting respiratory rebound after 16 hours anaerobiosis. The post-anaerobic respiration was more dependent on the oxygen tension than the pre-anaerobic respiration if referred to the normal rate shown at 21 per cent oxygen. But if the post-anaerobic rates were compared with the rates sustained pre-anaerobically at an identical oxygen tension, an approximately equal percentage increase was observed over a wide range of tensions.4. The implications of these observations and auxiliary observations dealing with the rate of the heart-beat under various conditions are discussed insofar as they shed ligh...

Influence of some Potential Molluscacides on the Oxygen Consumption of Australorbis glabratus.

The killing mechanisms of chemical compounds used in the control of harmful or obnoxious invertebrates are quite variable. The problem has been investigated to some extent for the case of insects, but no data whatever seem available for snails in general and the trematode-transmitting species specifically. The urgent need for new molluscacides, more potent than the much applied copper sulfate or similar substances, has led to a survey of the snail-killing properties of a variety of chemical compounds, the results of which will be reported elsewhere by Nolan and Mann. During this work a number of potential molluscacides was uncovered. These, as well as some inactive compounds, were studied by us in respect to their inhibitory effect on the oxygen consumption of Australorbis glabratus, the intermediate host of Schistosoma mansoni in the West Indies and South America.1