Hormonal aspects in the causation of human breast cancer: epidemiological hypotheses reviewed, with special reference to nutritional status and first pregnancy

Epidemiology of breast cancer has identified early age at menarche, late first pregnancy, low parity and late menopause as risk factors, but in addition genetic factors, height, weight and living in western countries play a significant role. The international variation in incidence is almost exclusively due to non-genetic factors. Hypotheses in prevention-oriented research are reviewed: 1. obesity-related oestrogen production as a stimulus of the tumour in postmenopausal women; 2. nutritional status and energy expenditure during puberty and adolescence, developed for fertility and fecundity and extended later to breast cancer; 3. reproductive life during early adulthood, age at first pregnancy and its specific effects on breast tissues. The message of preventability of breast cancer is that mammary epithelial differentiation should come early. Our insight concerning events in puberty and early adulthood can be consolidated in one concept on the risk of extended proliferation of breast epithelium during early adulthood in the absence of full differentiation induced by pregnancy. The combined effects of Western-type nutrition, lack of exercise and Western-type women's emancipation sets the stage for breast cancer already at a young age. Since it is unlikely that emancipated women in affluent societies will return to the original life-style of getting pregnant as soon as it is biologically possible, a novel daring way of protection has to be considered. Could a "Breast Differentiation Pill" be developed to offer protection?     

Immobilized isocrite dehydrogenase: some aspects of its catalytic, chemical and immunological properties

Isocitrate dehydrogenase from Azotobacter vinelandii has been immobilized on Sepharose 4B with an efficiency of between 60 and 75%. The immobilized enzyme is assayed by a flow technique which monitors a final steady state level of product formation. By the assay system described it is estimated that the immobilized enzyme retains between 30 and 40% of the catalytic activity of the free enzyme. Studies have been carried out on the substrate dependence of the enzyme. The enzyme requires magnesium ions with optimal concentrations of 10⁻³m and above. The dependence on isocitrate and TPN⁺ concentrations was determined and analyzed by double-reciprocal plots. The immobilized enzyme is inactivated by DTNB [5,5′-dithiobis(2-nitrobenzoic acid)] and reactivated by DTT (dithiothreitol). The DTNB-modified enzyme can be reactivated by potassium cyanide. Comparison of these reactions with those of the free enzyme suggest that the steric environment of the active site was not grossly altered by immobilization. Some supporting evidence is derived from the identity of the energies of activation, 16,600 cal/mole, of free and immobilized enzyme catalyzed oxidation of isocitrate. Furthermore, the immobilized enzyme is inactivated by antibody prepared against the free enzyme. The covalently attached enzyme is resistant to tryptic digestion except in the presence of 2 m urea. This suggests that exposed lysyl residues which may be the primary site of attack by trypsin are utilized in immobilization. Treatment of the enzyme with 2 m urea unfolds the enzyme to a conformation which has very little activity but which recovers full activity upon removal of the urea. Interaction of the enzyme with antibody suggest that the antibody reacts univalently. The second valence can be satisfied by addition of free enzyme. The free enzyme bound to the immobilized enzyme-antibody complex is active. Preliminary attempts to dissociate the enzyme-antibody complexes have been unsuccessful.     

Clinical, parasitological and immunological aspects of experimental infection with Trypanosoma evansi in dogs

This research investigated the pattern of antibody response by means of enzyme linked immunosorbent assay (Elisa) and indirect fluorescent antibody test (IFAT) through the course of experimental Trypanosoma evansi infection in dogs. Clinical and parasitological features were also studied. The average prepatent period was 11.2 days and parasitaemia showed an undulating course. Biometrical study of parasites revealed a mean total length of 21.68mm. The disease was characterized by intermittent fever closely related to the degree of parasitaemia and main clinical signs consisted of pallor of mucous membrane, edema, progressive emaciation and enlargement of palpable lymph nodes. Diagnostic antibody was detected within 12 to 15 days and 15 to 19 days of infection by IFAT and Elisa, respectively. High and persistent antibody levels were detected by both tests and appeared not to correlate with control of parasitaemia     

Biomechanical aspects of underwater acoustics with a special reference to hydrobiology

Some biomechanical aspects of the acoustical behaviour of underwater animals is discussed here. We have avoided mathematical complexities.     

Epidemiological and serological aspects in canine toxoplasmosis in animals with nervous symptoms

The presence of anti-Toxoplasma gondii IgM and IgG antibodies was studied in samples of blood serum taken from eighty dogs with nervous symptoms at the Servi?o de Enfermidades Infecciosas dos Animais, Faculdade de Medicina Veterinária e Zootecnia, Unesp, Botucatu, S?o Paulo, Brazil. The frequency of IgG titers were 16 (13.7%), 64 (13.7%), and 256 (5%), and for IgM titers were 16 (7.5%), 64 (15%), and 256 (8.7%). Positive reactions were more frequent in the older animals, males, from a rural environment, in constant contact with small animals, principally birds and rodents. There was a higher frequency of a positive reaction in dogs fed with kitchen food, especially in those fed with raw ingredients. The most common neurological pictures were alterations in consciousness, in movement, and in the hand-cart test. The percentage of reagents with specific IgM antibodies was high, indicating active infections, but the possibility of co-infection with the distemper virus can not be discarded, and this may be a predisposing factor for toxoplasmosis infection, once the distemper virus has a potent immunosuppressive action.     

Study of some epidemiological aspects of 253 cases of cryptococcosis.

Some epidemiological characteristics of 253 cases of cryptococcosis (CRY) diagnosed between 1981 and 1993 in the Mu?iz Hospital (MH) of Buenos Aires City, were studied. The incidence of CRY associated with AIDS (CRY+AIDS) in the MH during 1983-1993, could be divided into 3 periods: between 1983 and 1988 1-3 cases a year were diagnosed; during 1989-91, the number of cases dopubled annually and in 1992-93 the annual increment was lower. CRY associated with predisposing causes other than AIDS (CRY+non AIDS) exhibited an annual incidence of 0-3 cases during the whole period studied. CRY was more frequent in males (86%). The difference between sexes was more evident in CRY+AIDS patients (88% males) than CRY+non AIDS ones (65% males). The median age (MA) of the studied population was 28 (range 10-71) years; 27 (10-48) in women and 29 (17-71) in men. CRY+AIDS and CRY+non AIDS patients exhibited a MA of 29 (17-51) and 40 years (10-71), respectively. AIDS was the predisposing factor in 92% of patients; 65% of them were intravenous drug abusers and 22% homosexual males, with a MA of 27 (17-40) and 33 (23-55) years, respectively. Cryptococcus neoformans var. neoformans was isolated from all CRY+AIDS and 79% of CRY+non AIDS patients and the gattii variety (Serotype B) produced 4 (21%) cases of CRY+non AIDS.     

Developmental and immunological aspects of Drosophila-parasitoid relationships

The Drosophila-parasitic wasp (parasitoid) associations involve integrating adaptations of considerable complexity. This review focuses on some of the factors that influence these interactions including host immunity, nutrition and hormonal changes, and parasitoid virulence and mechanisms of immune suppression.