Search

The coagulation factors and components of the fibrinolytic system were examined in 31 women with a previous history of phlebographically-verified thrombosis during the use of oral contraceptives of the combined type. Special attention was given to the histochemically-determined fibrinolytic activator content of the wall of biopsy specimens of superficial veins. None of the patients was taking contraceptives at the time of the investigation. Pathological changes, particularly in the fibrinolytic defence system, were found in most of the patients. They may be regarded as predisposed to thrombosis, and one might wonder whether these patients would sooner or later have had their thrombosis even if they had not used contraceptives. The concentration of antithrombin III was normal, indicating that this test is of no value for detecting patients predisposed to thrombosis, who should preferably not take oral contraceptives.

A standard kit is prepared and distributed by WHO for testing insecticide resistance in adult mosquitos, and it would seem advantageous to be able to use the filter papers impregnated with DDT and dieldrin contained in this kit for testing resistance in other insects. Experiments have been successfully conducted with a view to developing methods based on the use of these papers for testing susceptibility levels in bed-bugs, cone-nosed bugs, fleas and lice. The designs of the various test methods and the results obtained are described in this paper. The tests for bed-bugs and fleas have been adopted as provisional methods by the WHO Expert Committee on Insecticides; those for cone-nosed bugs and lice have been designated tentative methods, requiring further investigation prior to the drawing up of specifications.

IT has been stated by Dorojkin1 that Solanum curtilobum and eight other South American species and varieties of Solanum are immune from Spongospora subterranea, the causal agent of powdery scab of potatoes; in this paper the number 8008 is linked with S. curtilobum, as are other numbers with the other Solanum species, and these are presumably the reference numbers of individual lines which were being used. Bukasov2 quotes Dorojkin and states that immunity from powdery scab has been established in S. curtilobum and the eight other species and varieties. This statement has been repeated by Hawkes3 and Black4, but in these papers no mention is made of the reference numbers of the individual lines concerned. It might be assumed, therefore, that S. curtilobum as such is immune, despite the fact that many lines or varieties of this species exist. That some of these lines at least do not carry immunity was shown by the following experiments.

Groups of young albino mice were fed continuously four different types of diets and were compared with regard to (1) rate of weight gain; (2) resistance to experimental bacterial infections. The protein content of the four diets was as follows: (a) pellets: a minimum of 21 per cent "crude" protein (according to the manufacturer); (b) diet 20 C: 20 per cent casein; (c) diet 8 C: 8 per cent casein; (d) diet 8 C + AA: 8 per cent casein supplemented with 12 per cent of a mixture of essential amino acids. All diets provided an adequate supply of minerals and vitamins. They were administered ad lib. Three strains of pathogens virulent for mice were used for the infection tests, namely: Staphylococcus aureus, Mycobacterium fortuitum, and Mycobacterium tuberculosis bovis. The bacteria were injected by the intravenous route. The experimental regimens were begun at different times before infection, and were continued until death of the animal, or until termination of the experiment. It was found that mice on the 8 C diet exhibited much greater susceptibility to infection than did mice on the 20 C diet; mice receiving pellets were intermediate between these two groups. The infection-enhancing effect of the 8 C diet could be entirely corrected by amino acid supplementation (diet 8 C + AA). Indeed, mice fed diet 8 C + AA proved the most resistant to infection. The fact that animals fed pellets (which contain a minimum of 21 per cent protein) consistently died faster following infection than did animals fed diets 20 C or 8 C + AA suggests that qualitative characteristics of the protein in the regimen are as important as the quantity of protein fed in determining susceptibility to infection. The differences in susceptibility exhibited by the mice on the four experimental diets were the same whatever the species of bacterial pathogen used for the infection test, the size of the infective dose, and the duration of the disease. There was no apparent relation between the effects of the diets on the weight curves of the animals, and on resistance to infection. Mice on diet 8 C (which were most susceptible) gained weight as rapidly as those on 20 C and more rapidly than those fed 8 C + AA (which were most resistant). All the tests reported in the present paper were carried out with young mice, which were placed on experimental diets within 1 to 2 weeks after weaning. Preliminary experiments suggest that the relation between dietary factors and susceptibility to infection was more difficult to bring out in older animals. There was evidence also that this relation was most apparent during the first weeks that the animals were fed the experimental diets, and became less striking after several weeks.

A survey of rinderpest-neutralizing antibody was carried out on the sera of 315 hippopotamuses which were shot in the Queen Elizabeth Park, Uganda. No serological positives were found in animals aged 11 years or less but about 4% were detected in the age class 13–25 years. In the 28–41 years age class the proportion of positives rose to about 36%. All except one of the positive sera were titrated, the figures obtained being comparable to those in other recently infected species of wild ungulates.It was concluded that the heat-stable antibody in hippopotamuses resulted from inapparent infections with rinderpest virus during epizootics which passed through the areas of Lake George and Lake Albert in the years 1920/21, 1931/33 and 1944/45. No record was available of clinically recognizable rinderpest in the hippopotamus population but deaths due to other causes were mentioned briefly.Comment was made on the stability of rinderpest-neutralizing antibody over periods of about 30 years.One of us (R. M. L) is grateful to the Nuffield Foundation for financial support. Thanks are due to Drs S. S. Stone and W. P. Heuschele (Agricultural Research Service, United States Department of Agriculture) for their assistance in organizing the collection of serum samples.This paper is published by permission of Mr H. R. Binns, C.M.G., O.B.E., Director, E.A.V.R.O.

Cells of the original line of lymphoma 6C3HED, which regularly prove susceptible to the effects of guinea pig serum in vivo, were cultured in Eagle's medium devoid of L-asparagine; after a latent period of 2 or more weeks, during which time the cell population declined markedly, some of the cells began to proliferate, and thereafter continued vigorous growth. On implantation into mice the proliferating cells were found, however, to have completely and permanently lost their susceptibility to the effects of guinea pig serum. By contrast, when cultures of the original line of 6C3HED cells were prepared in Eagle's medium to which L-asparagine was added in a concentration of 20.0 mg/liter or more, they proliferated vigorously from the beginning; after long periods of growth in the enriched medium in vitro they remained susceptible to the effects of guinea pig serum upon test in vivo. Other amino acids, purines, and pyrimidines were unable to substitute for L-asparagine in this relation. Furthermore, a variant subline of 6C3HED cells which had become insensitive to guinea pig serum under in vivo conditions did not require L-asparagine for growth in tissue culture. It seems plain from the findings as a whole, that in 6C3HED cells, L-asparagine dependence in vitro is associated with the in vivo character of guinea pig serum sensitivity, and conversely L-asparagine independent variants are insusceptible to the effects of guinea pig serum. The implications of the findings complement those of a companion paper in which direct evidence is provided that the L-asparaginase of guinea pig serum is responsible for its antilymphoma effects.

There have been several reports on the action of tannic acid upon red blood cells (1, 2). The present paper is concerned with observations indicating that tannic acid acts upon mammalian red blood cells, rendering them resistant to streptolysin-S, an oxygens'able hemolysin of Streptococcus pyogenes (3, 4), in such a manner that the lost susceptibility of the tanned cells can be readily restored by treating them with certain proteins.