Magdi M. Mashaly

Effect of melatonin and lighting schedule on energy metabolism in broiler chickens

The effect of melatonin and lighting schedule on energy metabolism in broiler chickens was studied. Eight groups of six female broiler chickens each were assigned to a continuous lighting schedule [23 h light (L):1 h darkness (D)] or an intermittent lighting schedule (1L:3D), and were fed a diet with or without melatonin (40 ppm). At 21 d of age, the chickens were placed in respiration chambers for 20 d. Energy and nitrogen balances, heat production, and physical activity were measured per group. The only effect of melatonin on energy metabolism, was a decreasing effect on activity-related heat production. The intermittent lighting schedule induced improved feed conversion, higher metabolizability of the diet, and lower physical activity compared to continuous lighting. No interactions between melatonin and lighting schedule were found on energy metabolism traits. Lighting schedule strongly affected daily heat production pattern (total, activity-related, and nonactivity-related heat production). Melatonin had a reducing effect on activity-related heat production during the day, especially during light periods. The present study demonstrated that reduced energy expenditure for physical activity, caused by the supplementation of melatonin to the diet, might be a reason for the often observed improvement of feed conversion. Furthermore, this study showed that feed conversion was improved with an intermittent lighting schedule, which was related to higher metabolizability and lower energy expenditure on physical activity, compared to continuous lighting.

Serum Testosterone Concentration During two Hours of Moderate Intensity Treadmill Running in Trained men and Women

The purpose of this study was to determine alterations in testosterone concentration in women during 2 hours of moderate intensity running, and to compare this response to that seen in men. Maximal oxygen uptake (VO2 max) and anaerobic threshold (AT) were determined in 11 men and 9 women. These subjects subsequently ran for 2 hours on a motor-driven treadmill at 10% below the AT which was approximately 70% VO2 max. Blood samples were drawn at 0, 30, 60, 90 and 120 minutes of exercise and testosterone was measured by specific radioimmunoassay. Serum testosterone concentration was significantly increased (41%, P less than .01) after 30 minutes of exercise in the men. In the women, testosterone was not significantly increased from pre-exercise concentrations until 120 minutes of exercise (48%, P less than .01). At this time the testosterone concentration in the men had decreased and was no longer significantly elevated from the pre-exercise concentration. The magnitude of the increases in serum testosterone concentration can probably be accounted for by decreases in the metabolic clearance rate of sex-steroids known to occur during exercise. Differences in the testosterone response between men and women during prolonged aerobic exercise are of interest and may imply that different mechanisms of control are involved.

Relationship between circulating thyroid hormones and cell-mediated immunity in immature male chickens

The objective of this experiment was to examine the relationship between circulating triiodothyronine (T3), thyroxine (T4) and cell-mediated immunity in immature male chickens. Three week old Single Comb White Leghorn male chicks were used as the experimental animals. In order to produce a wide range of circulating thyroid hormone concentrations, birds were divided into groups and received one of nine treatments including surgical thyroidectomy; 0.1% propylthiouracil (PTU) in the feed; 1 ppm T3 and 10 ppm T4 in the feed. The graft versus host (GvH) response and response to phytohemagglutinin (PHA) were measured at 6 weeks of age. Total and differential white blood cells were counted. Birds were bled, weighed, sacrificed, and the lymphoid organs were removed and weighed. Concentrations of T3 and T4 were measured in the birds from all treatment groups. There were positive correlations between thyroid hormones, mainly T3, and weights of thymus and spleen. T4 but not T3 was positively correlated with number of circulating lymphocytes. There were no significant correlations between circulating T3 and T4 and either PHA or GvH responses. It was concluded that physiological levels of thyroid hormones are needed to maintain normal weights of thymus and spleen and a normal level of circulating lymphocytes. Furthermore, we conclude that lower than physiological levels might be sufficient to maintain normal cell-mediated immunity. Finally, in order to enhance cell-mediated immune responses using thyroid hormones, different doses than were used might be required.

Effect of genetic selection and MHC haplotypes on lymphocyte proliferation and Interleukin-2 like activity in chicken lines selected for high and low antibody production against sheep red blood cells

Chickens from third generation matings of lines of chickens selected for high (HA) and low (LA) antibody production to sheep red blood cells (SRBC) and typed for MHC genotypes B13/13, B13/21, and B21/21 were used in this study. Chickens from both lines carried all the three genotypes B13/13, B13/21, and B21/21. To study T- and B-lymphocytes mitogenic activity, 12-week-old female chickens were injected intravenously with 0.2 ml of 9% SRBC and spleens were collected at 0, 6 h, and 6 day post-antigen injection (pAg). Isolated lymphocytes were incubated with either Concanavalin-A (Con-A) for T-cell activity, or Pokeweed mitogen (PWM) for B-cell activity and thymidine 3H uptakes were measured. To study the Interleukin-2 (IL-2)-like activity in the same lines and genotypes, splenic lymphocytes from 12-week-old chickens were passed through nylon wool columns to enrich the T-cell population. After a 24 h incubation with Con-A, the conditioned media (CM) were collected. The CM were tested for IL-2 like activity by determining whether they altered the proliferation of Con-A stimulated T cells. This proliferation effect was then compared to that of a reference conditioned media (RCM) prepared from K-strain birds and that were used as the standard for the assay. There was no significant difference (p > 0.05) in IL-2 like activity between HA and LA lines, however, the LA was significantly higher than HA (p < 0.05) in T- and B-cell mitogenic activity. The genotype B13/13 had significantly higher (p < 0.05) IL-2 like activity than the B21/21. The genotype B13/13 was also significantly higher (p < 0.05) in T- and B-cell mitogenic activity than the B21/21. At 0 h, pAg T- and B-mitogenic activity was significantly higher (p < 0.05) than 6 h. In summary, our results indicate that although the birds were selected for high antibody production to SRBC, their lymphocyte mitogenic activity was lower than those selected for low antibody production. Hence, humoral and cell-mediated immune responses appear to be under different genetic controls, and that selection for greater humoral response may be at the expense of cellular responses. Our results also suggest differences in IL-2 like activity production between chickens carrying different MHC B-haplotypes, and that genetic control of such activity is possibly linked to the MHC genes.

The role of neuroendocrine immune interactions in the initiation of humoral immunity in chickens

The presence of neuroendocrine immune interaction in mammalian species has been studied extensively and has been established. However, such an interaction is not as well established in avian species. Furthermore, the role of such an interaction in the initiation of humoral immunity is not well understood. Therefore, the present studies were conducted to determine mechanisms involved in the initiation of humoral immunity in chickens. Cornell K-strain White Leghorn immature male chickens were used for all the experiments. Changes in hormonal and leukocyte profiles after antigen stimulation were studied. The ability of different leukocytes to produce ACTH was also investigated. It was concluded that the first step in the initiation of humoral immunity after antigen exposure is the release of interleukin-1 by macrophages, which in turn stimulates the production of CRF by hypothalamus and/or leukocytes. It is important to mention that CRF production could also be a direct effect of antigen stimulation. The CRF will then stimulate ACTH production by anterior pituitary and/or leukocytes. In addition, CRF will directly enhance lymphocyte activities in the spleen. Corticosteroid production will be stimulated by ACTH and will cause redistribution of lymphocytes from circulation to secondary lymphoid organs such as the spleen for antigen processing and eventual production of antibodies against the invading antigens. Finally, both ACTH and corticosteroids will later act in a negative feedback manner to regulate and control the process of antibody production by inhibiting lymphocyte activities and/or reducing the responsiveness to different stimuli.

Changes in the profiles of circulating white blood cells, corticosterone, T3 and T4 during the initiation of humoral immunity in immature male chickens

Eight-week-old male White Leghorn chickens were injected intravenously with either 0.1 ml of Brucella abortus (BA) or saline. Blood samples were collected before injection, 1 hr, 3 hr, 6 hr, 12 hr, 24 hr, and then daily for the following 6 days after the injection. Total white blood cells (WBC), differential counts and corticosterone (CS), T3 and T4 levels were measured in all blood samples. These data represented the results obtained from the primary response. To obtain data for the secondary response, the same birds were injected 4 weeks following the first challenge and the same procedure was followed. During primary and secondary responses, circulating lymphocytes and monocytes decreased significantly 3 hr following BA injection and then increased steadily and reached a peak approximately 5 days post-BA injection, however, circulating heterophils increased significantly 6-12 hr and returned to normal levels 2 days post-BA injection. Serum corticosterone increased significantly 3 hr following BA injection. Serum T3 decreased significantly 3 to 12 hr then increased significantly 2 days following BA injection. There were no significant changes in any of the measurements following saline injection. Correlations between circulating hormones and white blood cells were calculated and are reported. These results indicate that an early step in the initiation of humoral immunity is probably an increase in serum CS. This increase in CS is followed by a decrease in circulating lymphocyte and monocyte numbers. These decreases may be the result of lymphocyte trapping in secondary lymphoid organs. This series of events may occur to modulate and activate the immune response.

Changes in blood and spleen lymphocyte populations following antigen challenge in immature male chickens

1. The effects of antigen (Ag) injection on the distribution of lymphocyte populations of Cornell K-strain male chickens were studied. 2. Two experiments were conducted. In the first, chickens were injected with Brucella abortus (BA), a purported T-independent antigen. In the second, chickens were injected with sheep red blood cells (SRBC), a T-dependent antigen. Peripheral blood lymphocytes (PBL) and spleen lymphocytes isolated at 0, 3, 6, 9, 12 and 24 h following Ag injection were stained with monoclonal antibodies (mAb) detecting B-lymphocytes, CD4+ and CD8+ cells. 3. B-lymphocytes in the blood or spleen showed no significant changes following either BA or SRBC injection. In contrast, CD4+ cells were decreased in the blood and increased in the spleen following BA and SRBC injections. CD8+ cells were decreased in both blood and spleen following BA injection but were unchanged in either blood or the spleen following SRBC injection. 4. These results indicate that there is a change in both spleen and circulating lymphocyte populations, especially T-helper cells, following Ag injection. T-helper cells are apparently the primary population involved in the initiation of humoral immunity.

Chicken growth hormone, triiodothyronine and thyrotropin releasing hormone modulation of the levels of chicken natural cell-mediated cytotoxicity

Newly hatched White Leghorn male chicks received dietary supplements of either Triiodothyronine (T3) or Thyrotropin Releasing Hormone (TRH) until 8 weeks of age. Chicken growth hormone (cGH) (10 micrograms/kg BW) was injected into different chicks twice daily for 1 week starting at 7 weeks of age. Separate groups received both T3 and cGH. Natural cell-mediated cytotoxic (NCMC) activity against different target cells was tested. It was found that cytotoxic activity in cells involved in NCMC against P815 mouse mastocytoma was stimulated by cGH alone or in combination with T3 (1 ppm). These findings indicate that cGH and T3 stimulate NCMC activity; and that the cells responsible for this activity may be Natural Killer (NK) cells.

Relationship between circulating thyroid hormones and humoral immunity in immature male chickens

The objective of this experiment was to examine the relationship between levels of circulating T3, T4, and humoral immunity in immature male chickens. Three week old Single Comb White Leghorn male chicks were used as the experimental animals. In order to produce a wide range of circulating thyroid hormone concentrations, birds were divided into groups and received one of nine treatments including surgical thyroidectomy; 0.1% propylthiouracil (PTU) in the feed; 1 ppm T3 and 10 ppm T4 in the feed. Antibody production against sheep red blood cells (SRBC) (thymus-dependent antigen) and Brucella abortus (BA) (thymus-independent antigen) was tested at 6 weeks of age. Concentrations of T3 and T4 were measured in birds from each treatment group at 7 and 11 weeks of age. At 11 weeks of age, birds were weighed, sacrificed and lymphoid organs removed and weighed. There were positive correlations between circulating thyroid hormones and weights of bursa of Fabricius and spleens. There were no significant correlations between circulating thyroid hormones and antibody production. It was concluded that physiological levels of thyroid hormones are needed to maintain normal weights of bursa and spleen. Furthermore, we conclude that lower than physiological levels might be sufficient for normal antibody production. Finally, stimulation of antibody production using thyroid hormones may require different doses than what were utilized in this study.

Initiation of humoral immunity. I. The role of cytokines and hormones in the initiation of humoral immunity using T-independent and T-dependent antigens

The early events during the initiation of immune responses following the injection of T-independent (lipopolysaccharide, LPS) and T-dependent (bovine serum albumin, BSA) antigens were studied in immature male chickens. Specifically, the role of cytokines and hormones in the initiation of humoral immunity against these antigens was investigated. Both interleukin-1 (IL-1) and tumor necrosis factor (TNF-alpha) increased significantly post-LPS but not post-BSA injection. While interleukin-2 (IL-2) significantly decreased post-LPS injection, IL-2 significantly increased post-BSA injection. Furthermore, corticosterone levels significantly increased and tri-iodothyronine (T(3)) levels significantly decreased post-LPS but not post-BSA injection. In this study, the results indicate that although LPS and BSA can induce a humoral antibody response in chickens, they activate different cytokines and neuroendocrine network systems.