Sources, Effects and Risks of Ionizing Radiation

Background The rates of colon cancer in various countries are strongly correlated with the per capita consumption of red meat and animal fat and, to a lesser degree, inversely associated with the consumption of fiber. Methods We conducted a prospective study among 88,751 women 34 to 59 years old and without a history of cancer, inflammatory bowel disease, or familial polyposis who completed a dietary questionnaire in 1980. By 1986, during 512,488 person-years of follow-up, 150 incident cases of colon cancer had been documented. Results After adjustment for total energy intake, animal fat was positively associated with the risk of colon cancer (P for trend = 0.01); the relative risk for the highest as compared with the lowest quintile was 1.89 (95 percent confidence interval, 1.13 to 3.15). No association was found for vegetable fat. The relative risk of colon cancer in women who ate beef, pork, or lamb as a main dish every day was 2.49 (95 percent confidence interval, 1.24 to 5.03), as compared with those reporting consumption less than once a month. Processed meats and liver were also significantly associated with increased risk, whereas fish and chicken without skin were related to decreased risk. The ratio of the intake of red meat to the intake of chicken and fish was particularly strongly associated with an increased incidence of colon cancer (P for trend = 0.0005); the relative risk for women in the highest quintile of this ratio as compared with those in the lowest quintile was 2.49 (95 percent confidence interval, 1.50 to 4.13). A low intake of fiber from fruits appeared to contribute to the risk of colon cancer, but this relation was not statistically independent of meat intake. Conclusions These prospective data provide evidence for the hypothesis that a high intake of animal fat increases the risk of colon cancer, and they support existing recommendations to substitute fish and chicken for meats high in fat.

https://www.nejm.org/doi/pdf/10.1056/NEJM199012133232404

Relation of meat, fat, and fiber intake to the risk of colon cancer in a prospective study among women.

The bursa of Fabricius and the thymus are "central lymphoid organs" in the chicken, essential to the ontogenetic development of adaptive immunity in that species. Surgical removal of one or both of these organs in the newly hatched chicken, followed by sublethal X-irradiation the next day, has permitted recognition of two morphologically distinct cell systems in the "peripheral lymphoid tissues" of the spleen, gut, and other organs, and clear definition of the separate functions of each cell system.

The thymus-dependent development is represented morphologically by the small lymphocytes of the circulation and the white pulp type of development in the tissues. As in mammals, the thymus-dependent tissues of the chicken are basic to the ontogenesis of cellular immunity: graft versus host reactions, responses of delayed hypersensitivity and homograft rejection; and play a less clearly defined role in the antibody response to at least some antigens. Thymectomized-irradiated chickens are deficient in all these responses, and grow more slowly than any of the other experimental groups. In these animals germinal centers, plasma cells, and capacity for immunoglobulin synthesis remain intact.

The bursa-dependent development is represented morphologically by the larger lymphocytes of the germinal centers and the plasma cells, and functionally by the immunoglobulins. Bursectomized-irradiated chickens are agammaglobulinemic and unable to produce detectable antibody despite intense, repeated stimulation with bovine serum albumin and Brucella abortus organisms. The thymus-dependent development in these animals seems to be normal; they have adequate numbers of lymphocytes in the circulation and tissues, are able to reject skin homografts, though more slowly than usual, and to exercise graft versus host reactions. The short life span of these chickens has precluded adequate study of responses of delayed hypersensitivity.

There was no evidence of significant impairment of reticuloendothelial function in either the bursectomized-irradiated or the thymectomized-irradiated group, as judged by the clearance of colloidal gold and I131-tagged keyhole limpet hemocyanin.

/pdf/the-functions-of-the-thymus-system-and-the-bursa-system-in-4fsv3apx1v.pdf

The functions of the thymus system and the bursa system in the chicken

INTRODUCTION.......................................................... 390 GNOTOBIOTIC TERMINOLOGY AND CRITERIA............................ 392 THE MICROBIAL ASSOCIATES............................................. 393 Development and Characteristics of the Normal Flora............................. 393 Attempts to Establish a Microbial Flora in Germ-Free Animals.................... 395 Dietary Effects ......................................................... 396 Effects of Closed Environment................................................. 397 Factors Affecting Microbial Passage into the Host............................... 397 THE ANIMAL HOST: GERM-FREE OR MODIFIED BY MICROBES..... .... 398 Nutrition, Digestion, and Metabolism.......................................... 398 Rats and mice.......................................................... 398 Other animal species....................................................... 400 Structure and Function of Various Organ Systems............................... 401 Cardiovascular systems..................................................... 401 Gastrointestinal tract (upper segments) ........... ............................ 402 Enlarged cecum of germ-free rodents......................................... 402 Other autocoid substances of the germ-free intestine............................ 403 Water absorption inhibition in the germ-free lower bowel....................... 403 Other organ systems....................................................... 404 Body Defenses.......................................................... 404 Cells, tissues, and organs associated with defense functions ...... .................. 405 Humoral defensive elements................................................. 406 Immune responses ......................................................... 407 Tissue Repair.......................................................... 410 Survival and Aging.......................................................... 410 THE GNOTOBIOTIC ANIMAL IN THE STUDY OF DISEASE................ 411 Shock, Intestinal Obstruction, and Thermal Trauma.............................. 411 Wasting Syndrome .......................................................... 412 Oral Diseases.......................................................... 413 Dental caries .......................................................... 413 Periodontal disease........................................................ 414 Enteric Infections .......................................................... 414 Ulcerative Colitis.......................................................... 416 Uremia.................................................................... 416 Mycoplasmosis .......................................................... 417 Tuberculosis................................................................ 417 Yeast Infections.......................................................... 418 Protozoal Infections......................................................... 418 Amebiasis .......................................................... 418 Histomoniasis............................................................. 419 CONCLUSION.............................................................. 419 LITERATURE CITED........................................................ 420

The gnotobiotic animal as a tool in the study of host microbial relationships.

Publisher Summary The chapter focuses on the developmental aspects of immunity. The ontogenetic development of immune responses in the immature animal and the developmental cellular stages of the immune response in the adult animal are discussed in this chapter. The cellular mechanisms underlying the several immune responses have not received the full attention either to the evolutionary principles underlying the development of all biological systems or to the broad biological rules that govern the proliferative and differentiate activities of cells in any biologically functioning system. The chapter reviews the immunological status of fetal and neonatal mammals as well as several aspects of the ontogeny of the immune response when examined by the most sensitive technique presently available. Developmental stages of immune reactions and their mutual relationships such as relationship of phagocytosis to specific cellular reactions, relationship of delayed hypersensitivity to antibody formation, and dynamics of antibody formation are also presented in this chapter. The increase of immunological capacity with age and the appearance of natural antibodies result solely from specific antigenic stimulation; the chapter discusses the Unitarian concept of cell differentiation and proliferation underlying any form of immunological response. Several methods for studying developmental aspects of immunity and immunological development are also discussed in this chapter.

Developmental aspects of immunity.

: Germfree CFW mice exposed to 3 kR of whole-body X-irradiation have a mean survival time of 7.3 days, whereas conventional CFW mice under the same conditions have a mean survival time of 3.5 days. The increased survival time in germfree mice is ascribed to the longer life span of mucosal cells. The migration of epithelial cells from crypt to villus tip takes 4.3 days in germfree mice and 2.1 days in conventional mice. After 3 kR, the intestine is denuded in 3.5 days in conventional mice and not until 7 days in germfree mice. Death occurs very soon after denudation in both groups. (Author)

The intestinal mucosa of germfree mice after whole-body x-irradiation with 3 kiloroentgens.

SummaryWhen germfree mice are fed a diet supplemented with cholic acid, the turnover of intestinal mucosal cells is reduced from 4.44 to 2.12 days, which is the turnover time in conventional mice. It is concluded that cholic acid, which is produced in conventional mice by hydrolyzing enzymes of bacterial origin, has a regulatory effect on intestinal mucosal cell turnover.

Increased turnover of intestinal mucosal cells of germfree mice induced by cholic acid.

SummaryNeonatally thymectomized mice develop a characteristic wasting disease from 4 weeks to 4 months after thymectomy; no pathogenic bacteria have been isolated from these animals that can be obviously incriminated as the cause of the syndrome. Germ-free: thymectomized mice exhibit none of the symptoms of this disease in 8 months, the maximum period of observation to date.Upon contamination the ex-germfree mice, thymectomized at birth, develop the disease within 4-8 weeks, though those thymectomized at 44-51 days do not develop the disease upon contamination and subsequent conventionalization.

The absence of wasting in thymectomized germfree (axenic) mice.

SummaryGermfree and conventional CFW mice were evaluated for elevations in serum CSF levels at varying time intervals after 850 R whole body irradiation. Conventional mice showed elevations of CSF levels on Days 6–9 while sera from germfree mice were inactive on Days 1–10. The data suggests that the bacterial flora of the gut play a role in the elevations of serum CSF seen after irradiation.The technical assistance of Mrs. Mildred Rosen-field is gratefully acknowledged.

Serum Colony Stimulating Factor Levels in Irradiated Germfree and Conventional GFW Mice

The treatment of X-irradiated germfree CFW and C3H mice with isologous and homologous bone marrow

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