Enterotoxin production by Vibrio cholerae and Vibrio mimicus grown in continuous culture with microbial cell recycle

We have examined the effect of complete cell recycle on the production of cholera toxin (CT) by Vibrio cholerae and CT-like toxin by Vibrio mimicus in continuous culture fermentations. Complete cell recycle was obtained by filtering culture fluids through Amicon hollow fibers with an exclusion limit of 100,000 daltons (H1P100-20) and returning the concentrated cell slurry to the fermentor. A single 1-liter laboratory fermentor system modified with this recycle loop was capable of producing over 20 liters of cell-free culture filtrate per day. Toxin production in this system was compared with yields obtained in traditional continuous cultures and in shake flask cultures. Yields of CT from V. cholerae 569B in the recycle fermentor were highest at the highest dilution rate employed (1.0 vol/vol per h). The use of complete cell recycle dramatically increased yields over those obtained in continuous culture and equaled those obtained in shake flasks. The concentration of CT in the filtrate was slightly less than half of that measured in culture fluids sampled at the same time. Similarly, V. mimicus 61892 grown in the presence of 50 micrograms of lincomycin per ml produced 280 ng of CT per ml in the recycle fermentor, compared with 210 ng/ml in shake flasks under optimal conditions. The sterile filtrate from this fermentation contained 110 ng/ml.     

Predation of Arternia cysts by water-tiger larvae of the genus Anacaena (Coleoptera,Hydrophilidae)

Artemia cysts are preyed upon by the larvae of Anacaena (Coleoptera, Hydrophilidae) in the wet supralittoral of the hypersaline Solar Lake near Elat. The larvae are specialized feeders of the cysts, as shown by laboratory experiments.     

Leukocyte migration inhibition test in breast cancer patients treated with conventional therapy or with conventional therapy plus poly A · poly U

Summary Leukocyte migration inhibition tests (LMIT) were performed to measure the immunologic reactivity of patients with initially operable breast cancer. Leukocyte migration was inhibited in 38% of 159 patients in the presence of autologous tumor extract, in 33% of 160 subjects in the presence of autologous serum, and in 47% of 148 patients in the presence of extract and serum. These patients formed part of a randomized clinical trial comparing conventional treatment complemented by injections of poly A · poly U with conventional treatment and injection of saline as a placebo.A sequential study was carried out, testing the leukocyte reactivity 7 days, 2 months, 4 months, and 1 year after the operation. The percentage of patients with positive LMIT increased significantly with time. Statistical comparison revealed no significant difference in the reaction of the two therapeutic groups. In addition, no significant difference was found between those with lymph node involvement and those without, although the percentage of positive LMIT in the presence of tumor extract appeared to be higher in the second group 1 year after surgery. Radiotherapy given to those with lymph node involvement did not significantly change their reaction.This study also confirmed the presence in some autologous sera of a synergistic factor (SS factor) that increased the inhibition of migration of leukocytes by autologous tumor extract. This factor was found in 18 patients, who were equally distributed between the two therapeutic groups.In the group with synergistic factor, the percentage with lymph node involvement appeared greater (83% compared with 68% among those patients who had no SS factor), and the incidence of distant metastases was also raised (44% compared with 21%). This factor seemed to indicate a poor prognosis. Moreover, there was a difference in the results between the two therapeutic groups in patients with synergistic factor. Of nine patients undergoing conventional treatment, six developed metastases, whereas only two of the nine patients also receiving poly A · poly U developed metastases. The same trend was observed throughout the trial population.     

Plasmodium falciparum: inhibition in vitro with lactoferrin, desferriferrithiocin, and desferricrocin

The microbial iron chelators desferriferrithiocin and desferricrocin as well as human lactoferrin were tested in vitro against Plasmodium falciparum. The microbial chelators inhibit the growth of P. falciparum in a dose dependent way. Parasite multiplication is stopped at 25-30 microM desferriferrithiocin, whereas 60-90 microM desferricrocin are needed to exhibit the same effect. After iron saturation, the microbial chelators are ineffective. Human lactoferrin (30 microM), both iron free and iron saturated, inhibits P. falciparum. A 3-day preincubation of host erythrocytes with iron free and iron saturated lactoferrin prior to infection enhances this effect, which is therefore attributed to lactoferrin bound iron. It has been suggested that the lactoferrin/iron complex generates oxygen free radicals, which may cause membrane damage of both erythrocyte and parasite. This process can be considered to lead to growth inhibition of the parasite.