FOOD SAFETY ISSUES IN CANADA

Food Consumption/Nutrition/Food Safety,

Causally Symmetric Bohm Model

The aim of this paper is to construct a version of Bohm’s model that also includes the existence of backwards-in-time influences in addition to the usual forwards causation. The motivation for this extension is to remove the need in the existing model for a preferred reference frame. As is well known, Bohm’s explanation for the nonlocality of Bell’s theorem necessarily involves instantaneous changes being produced at space-like separations, in conflict with the “spirit” of special relativity even though these changes are not directly observable. While this mechanism is quite adequate from a purely empirical perspective, the overwhelming experimental success of special relativity (together with the theory’s natural attractiveness), makes one reluctant to abandon it even at a “hidden” level. There are, of course, trade-offs to be made in formulating an alternative model and it is ultimately a matter of taste as to which is preferred. However, constructing an explicit example of a causally symmetric formalism allows the pros and cons of each version to be compared and highlights the consequences of imposing such symmetry. In particular, in addition to providing a natural explanation for Bell nonlocality, the new model allows us to define and work with a mathematical description in 3-dimensional space, rather than configuration space, even in the correlated many-particle case

Leprosy: a review of the subject based on work at the Lady Willingdon Leper Settlement Chingleput, South India

From November 1933 until the end of 1935 I acted as Chief Medical Officer of the Lady Willingd.on Leper Settlement, Chingleput, South India, During that time I have been able to examine, study, and treat a large number of cases of leprosy. I have also been able to examine the records of an even greater number of patients who have been through this institution during the ten years from 1925 to 1935. It is on this experience and study that I base this thesis

Studies on the genus Bordetella

The genus Bordetella as defined by Lopez (1952) consists of the three organisms Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica. These species were formerly classified in the genus Haemophilus, but their inclusion in a new genus was suggested on the grounds of cultural and antigenic differences from other Haemophilus species.Bord. pertussis was first isolated by Bordet and Gengou (1906) from children suffering from the disease known as whooping cough. Eldering and ILendrick (1937) isolated a second organism, Bord. hparapertussis, which was also a cause of whooping cough, although the infection was generally of a mild type. The third member of the genus, Bord. bronchiseptica, has frequently been found in respiratory -tract infections of rabbits, guinea igs, cats and dogs and has also been isolated from a few cases of whooping cough (Brown, 1926; Medical esearch Council, 1951). The isolation of these species has never been easy, even using complex edia rendered selective by the addition of penicillin, and few diagnostic laboratories obtain igh percentage isolations of Bordetella strains from cases of whooping cough. Problems are also encountered in the laboratory culture of Bord. ertussis. This organism is difficult to grow and maintain in a virulent state, but the other two species are rriore easily grown and can be cultured on most,simple laboratory media. Cultur problems are also reflected in vaccine production.Whooping cough in young children causes high morbidity and since the discovery of the causal organisms, attempts have been made to develop suitable prophylactic agents. Whole cell vaccines are commonly used but possess many disadvantages, the most serious being the occasional occurrence of encephalopathy following vaccination. L1uch research has been carried out to obtain a satisfactory prophylactic material, without such disadvantages.The present work is an attempt to prepare a medium giving optimal growth of virulent Bord. pertussis, and, using this medium, to obtain a better knowledge of the chemical and immunological properties of Bord. pertussis antigens. An attempt is also made to clarify some of the antigenic relationships within the genus, using modern techniques of serological analysis such as gel diffusion and immunoelectrophoresis.A historical introduction to the work is presented, to show the difficulties which earlier workers have encountered with this genus and to give an outline of our present knowledge.1). A liquid medium supporting growth of virulent Bordetella pertussis has been described. It contains casamino acids, nicotinamide, glutathione tris buffer and inorganic salts as well as an anion exchange resin. The medium is reproducable, giving good yields of bacteria and is also cheap and easy to prepare. After the resin has been removed by decantation or filtration, the medium contains only dialysable components. Cells grown in this medium produce haemagglutinin and protective antigen. The liquid medium can be solidified by the addition of agar and then compares favourably with Bordet- Gengou medium for the growth of Bordetella species.2). The protective activity of Bordetella pertussis cells grown in tris -resin medium was assayed by intracerebral challenge in mice and was shown to reside in the cell wall. The activity was not destroyed by treatment of the cell wall with trypsin, lipase or detergent, although these removed adherant cytoplasmic material and trypsin destroyed the histamine -sensitising factor. The lipopolysaccharide moiety of the cell wall had no major role in protection.3). The lipopolysaccharides from Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica showed some chemical similarities, containing hexosamine, heptose and hexose in varying proportions. The lipopolysacch- -arides were species specific, but that isolated from Bord.pertussis was present in virulent and avirulent strains.4). Agglutination tests showed some similarities between strains of the same Bordetella species. Precipitation tests in agar gel revealed a large number of antigens common to all three species. The only antigens which could be identified were the species specific lipopolysaccharides. Two antigens were found to be common to the Bordetella and Haemophilus genera.5). Soluble haemagglutinins were prepared from Bord. Pertussis and Bord. parapertussis. They were reversibly inactivated by oxygen and all activity was rapidly lost on dialysis. They were destroyed by the proteolytic enzyme trypsin. An inhibitor to haemagglutination was found in cooked meat medium, and an inhibitory material, removable by treatment with neuraminidase, was found on ox erythrocytes. Most red cell species were agglutinated to the same titre.6). Two previously unknown pigments have been isolated from Bordetella species. A blue pigment, for which the name azurin is suggested, has been obtained from virulent strains of all three species. Azurin is a protein of low molecular weight, approximately 16,500, containing copper (0.156%). It has absorption maxima at 280 mμ and 625 mμ in the oxidised form, but the peak in the visible wavelengths disappears on reduction with cysteine or thioglycollate. Azurin is autoxidisable.A cytochrome of the c type has been isolated from Bord.pertussis and Bord. bronchiseptica. It has absorption maxima at 408 mµ in the oxidised form and at 416 mµ, 522 mμ. and 550 mp, in the reduced form. The method used for the purification of the bacterial cytochrome could also be applied to mammalian cytochrome c