Differential effects of experimental hyperthyroidism on declined immunity of broiler chicken.

Thyroid hormones (THs) are involved in the development of lymphoid organs and regulation of immune function in birds. However, their role as an immune-modulator in the hyperthyroid state is still debatable. To explore the interrelationship of thyroxine (T4 ) and the immune system, chicks were divided into three groups. Group I was comprised of control birds, who received the basal diet while group II and III were given diets supplemented with 5 µg and 10 µg thyroxine/kg feed, respectively, from 15 to 28 days of age. Cell-mediated immune response was evaluated through in vitro abdominal macrophage phagocytosis assay, macrophage nitric oxide (NO) production, heterophil-to-lymphocyte (H:L) ratio and delayed-type hypersensitivity response against phytohemagglutinin (PHA). Humoural immune response was assessed through serum IgG and IgM antibody production against sheep red blood cells (SRBCs) and antibody production against infectious bronchitis virus (IBV). Sampling was carried out at 7, 14 and 21 days of treatment. Results have shown higher levels (p < .001) of circulating T4 in both treatment groups compared to the control group. There was a lower (p < .05) macrophage engulfment percentage, an increase in H:L ratio (p < .001) in treated birds, while their NO production remained higher (p < .05) in thyroxine supplemented groups after bacterial lipopolysaccharide stimulation. The humoural immune response revealed a significant decline (p < .001) in IgG, IgM antibody production against SRBCs but IBV circulating antibodies increased with age. In conclusion, hyperthyroidism has a strong co-relation with decreased immune performance of birds.

Ontogenic development of corticotrophs in fetal buffalo (Bubalus bubalis) pituitary gland.

To evaluate the subpopulation of corticotrophs in developing buffalo (Bubalus bubalis) fetus, recovered pituitary glands (n=6 per group) from late first, second and third gestational female buffalo dams. The corticotrophs were identified by using specific antibodies against proopiomelanocortin (POMC) and adrenocorticotrophic hormone (ACTH) through immunohistochemistry. There was a significant (P≤0.05) increase of immunoreactive (ir) ir-ACTH cells during late 2nd trimester while, ir-POMC cells were more (P≤0.05) at late 3rd trimester of gestation as compared to other age groups. The quantity of co-localized cells for POMC and ACTH was significantly (P≤0.05) greater at the end of 1st gestation rather than 2nd and 3rd gestational fetal adenohypophyseal cells. This study is the first to demonstrate co-localization of POMC+ACTH and the affect of gestational age on the expression of these cells in buffalo fetus adenohypophysis.

Somatotrophs and lactotrophs: an immunohistochemical study of Gallus domesticus pituitary gland at different stages of induced moult.

The objective of this study was to determine the distribution of somatotrophs and lactotrophs and conduct a morphometrical analysis of immunoreactive somatotrophs and lactotrophs in the pituitary glands of White Leghorn Hens (Gallus domesticus) during the period of induced moult. We divided the periods of induced moulting into three phases viz. 7, 14 and 21 days. The labeled alkaline-phsphatase method with anti-GH (growth hormone) and anti-PRL (prolactin) as a primary antibody was used to detect somatotrophs and lactotrophs, in the midsagital sections of chicken adenohypophysis. Immunohistochemistry showed that somatotrophs are not only confined to the cephalo-caudal axis but can also be found in the caudal lobe; while lactotrophs were distributed in both lobes of the anterior pituitary gland at all stages of moulting (7, 14 and 21 days). Lactotrophs were of different shapes but somatotrophs were oval to round in morphology. At the given stages of induced moulting, some hypertrophied lactotrophs were also present after 7 days of induced moult in the anterior pituitary gland. However, there were moulting-related changes: from 7 to 21 days of induced moulting the immunoreactive-PRL cell population decreased, while the mean lactotroph size was more than that of somatotrophs. Basic quantitative and morphological information relating to somatotrophs and lactotrophs during the period of induced moult in laying hens is reported here and the changes brought about by induced moulting are restricted to PRL positive cells rather than GH positive cells.

Comparison of the fast-induced and high dietary zinc-induced molting: trace elements dynamic in serum and eggs at different production stages in hens (Gallus domesticus).

A number of 252, 70 week old, single comb white leghorn hens at the end of their first production cycle were divided into two groups: group-I; molted by fasting and group-II; by high dietary zinc to obtain the second and third production cycle. Sampling was carried out at 5%, peak and end of the second production cycle and at 5% and peak of the third production cycle. Serum zinc decreased at the peak of the second production cycle, while increased at the 5% of the third production cycle in zinc-molted group. Serum copper and manganese increased at the 5% and peak of the second production cycle in zinc-molted group. Egg albumin zinc and copper increased at the 5% and peak of the second as well as third production cycles in zinc-molted group. Egg albumin manganese increased at 5% during the second production cycle in fasting molted group. Egg yolk zinc increased at the peak of the second production cycle in zinc-molted group. Egg yolk copper increased at the 5% of second production cycle but decreased during the third production cycle in zinc-molted group. Egg yolk manganese increased at the 5% and at the end of the second production cycle in zinc molted group. Egg yolk manganese and iron decreased during the third production cycle in zinc-molted group. Eggshell zinc decreased at the end of the second production cycle in the zinc-molted group, while eggshell copper increased at the peak of the second as well as third production cycles in fasting molted group.

Changes in luteinizing hormone-containing gonadotrophs after moulting induced by fasting and zinc in laying hens (Gallus domesticus).

The purpose of the present study was to investigate egg production performance, immunohistochemical (IHC) identification, localization and morphological characterization of moulted hen's pars distalis luteinizing hormone (LH) gonadotrophs. This system has been validated for chicken LH by immunodetection of purified hormones on dot blots, western blotting and by specific labelling of cells on sagittal sections of chicken pituitaries. This study showed that egg production and egg weight increased significantly after zinc-induced moult when compared with fasting-induced moult. Luteinizing hormone-gonadotrophs are of numerous shapes and distributed throughout the adenohypophysis, with densely populated regions on the margins of pars distalis. Moulting of laying hens was associated with a significant increase in immunoreactive LH gonadotroph cell count and cell size, which peaked at the subsequent production stages. Zinc-induced moulting also caused a significant increase in LH gonadotroph cell size as compared with fasting-induced moulting. The nuclear size of LH-positive cells was distinct during decreased egg production. Our results validate the use of ovine LHbeta antibodies for the IHC localization of chicken LH gonadotrophs. This technology was further applied to the characterization of the shape and morphological changes of gonadotrophs as a function of the egg production status of the birds.