The regulation of plasma thyroid hormones in poultry

The way in which environmental and physiological factors regulate the plasma concentrations of thyroid hormones in birds has been investigated.The administration of goitrogens in the diets of growing chickens was found to depress the levels of plasma T„ and T, and increase the activity of the thyroid follicular cells.Daily rhythms in the levels of plasma T₃ and T₄ were found to be inversely related and independent of the circadian system and the pineal gland. The concentration of plasma T₃„ increased from its lowest levels at the onset of a light period and was associated with an increase in heart rate and a decrease in the concentration of plasma T₄ . Fasting abolished the daily rhythms in plasma thyroid hormones and was associated with a decrease in the concentration of plasma T₃ and an increase in the concentration of plasma T₄, while feeding, regardless of the time of day and photoperiod, resulted in an increase in the concentration of plasma T₃ and a decline in plasma T₄.Ducks transferred to a long day photoperiod showed an increase in the concentration of plasma T₄ during the refractory period of the breeding cycle which coincided with the post-nuptial moult. The initiation of photorefractoriness and moult in the W.illow Ptarmigan were not associated with any marked fluctuations in plasma T₃ and T₄, In quail the concentration of plasma T₄ responded to changes in daylength while the levels of both T₃ and T₄ were affected by the reproductive state of the bird.The concentration of pituitary TSH in ducks was affected by changes in thyroid status: goitrogens increased whereas injections of T₄ decreased levels of TSH as measured by immunocytochemistry and bioassay. Injection of TSH into laying hens was shown to increase the levels of both plasma T₃ and T₄.Elevated levels of plasma thyroid hormones were found during the first weeks of life, which declined as the birds became sexually mature. The concentration of plasma T₃ increased in broody bantam hens within one or two days after hatch and rose further after the chicks hatched. An injection of prolactin into hens increased the concentration of plasma T₃.The stress of repeatedly handling chickens and turkeys resulted in a decrease in the levels of plasma T₄ whereas temperature and dehydration stress affect the concentrations of T₄. and T₃ principally by a change in food intake.A reduction in the levels of plasma induced by thyroidectomy, fasting or by an increase in environmental temperature was associated with a decrease in the rate of heat production. An injection of into thyroidectomised birds resulted in a sustained increase in the levels of plasma T₃.The concentration of plasma triglycerides were found to be positively correlated with the levels of plasma T₃. Plasma lipoproteins were demonstrated to bind both T₃ and T₄.Plasma levels of T₄ were not useful for prediction of subsequent egg production in pedigreed hens and neither were the concentrations of plasma T₃„ and T₄ related to shell quality as measured by specific gravity and gas conductance. A relationship was established between the levels of plasma T₃ and improper healing of the navel in selected lines of newly hatched chicks

X chromosomes Aneuploidy Lymphocytes Centromeres Chromosomal translocations Sex chromosomes Etiology Fluorescent in situ hybridiz

Humans, birds, and some primates do not express the uric acid degrading enzyme urate oxidase (UOX) and, as a result, have plasma uric acid concentrations higher than UOX expressing animals. Although high uric acid concentrations are suggested to increase the antioxidant defense system and provide a health advantage to animals without UOX, knockout mice lacking UOX develop pathological complications including gout and kidney failure. As an alternative to the knockout model, RNA interference was used to decrease UOX expression using stable transfection in a mouse hepatic cell line (ATCC, FL83B). Urate oxidase mRNA was reduced 66% (p \u3c 0.05) compared to wild type, as measured by real time RT-PCR. To determine if UOX knockdown resulted in enhanced protection against oxidative stress, cells were challenged with hexavalent chromium (Cr(VI)) or 3-morpholinosydnonimine hydrochloride (SIN-1). Compared to wild type, cells with UOX knockdown exhibited a 37.2 ± 3.5% reduction (p \u3c 0.05) in the electron spin resonance (ESR) signal after being exposed to Cr(VI) and displayed less DNA fragmentation (p \u3c 0.05) following SIN-1 treatment. Cell viability decreased in wild type cells (p \u3c 0.05), but not cells with UOX knockdown, after treatment with SIN-1. These results are consistent with an increased intracellular uric acid concentration and an increased defense against oxidative stress

Urate oxidase knockdown decreases oxidative stress in a murine hepatic cell line

Humans, birds, and some primates do not express the uric acid degrading enzyme urate oxidase (UOX) and, as a result, have plasma uric acid concentrations higher than UOX expressing animals. Although high uric acid concentrations are suggested to increase the antioxidant defense system and provide a health advantage to animals without UOX, knockout mice lacking UOX develop pathological complications including gout and kidney failure. As an alternative to the knockout model, RNA interference was used to decrease UOX expression using stable transfection in a mouse hepatic cell line (ATCC, FL83B). Urate oxidase mRNA was reduced 66% (p < 0.05) compared to wild type, as measured by real time RT-PCR. To determine if UOX knockdown resulted in enhanced protection against oxidative stress, cells were challenged with hexavalent chromium (Cr(VI)) or 3-morpholinosydnonimine hydrochloride (SIN-1). Compared to wild type, cells with UOX knockdown exhibited a 37.2 ± 3.5% reduction (p < 0.05) in the electron spin resonance (ESR) signal after being exposed to Cr(VI) and displayed less DNA fragmentation (p < 0.05) following SIN-1 treatment. Cell viability decreased in wild type cells (p < 0.05), but not cells with UOX knockdown, after treatment with SIN-1. These results are consistent with an increased intracellular uric acid concentration and an increased defense against oxidative stress

Refinement of Biomarker Pentosidine Methodology for use on Aging Birds

There is no reliable method for determining age for most species of long-lived birds. Recent success using the skin chemical pentosidine as a biomarker has shown promise as an aging tool for birds. Pentosidine levels have been determined only from the breast tissue of carcasses, and we sought to refine the procedure with respect to biopsy size and location for safe and effective use on living birds. We compared pentosidine concentrations in 4 skin-size samples (4, 6, 8, and 20-mm diameter biopsies) from the breast of black vulture (Coragyps atratus) carcasses. We also compared pentosidine levels from breast and patagial tissue to document potential differences among collection sites of deceased vultures (with unknown ages) and monk parakeets (Myiopsitta monachus; with actual, minimal, and unknown ages). Pentosidine concentrations (pmol pentosidine/mg collagen) were similar among the 4 sizes of vulture breast skin (P = 0.82). Pentosidine concentrations for the breast (x̄ = 8.9, SE = 0.55, n = 28) and patagium (x̄ = 8.9, SE = 0.51, n = 28) of vultures were similar, but in parakeets, pentosidine was higher in the breast (x̄ = 15.9, SE = 1.30, n = 105) than the patagium (x̄ = 11.5, SE = 1.10, n = 105). We made pentosidine-based age estimates for vultures and parakeets using a general age curve for wild birds. We also made vulture age estimates using plumage characteristics and a cormorant (Phalacrocorax auritus) age curve. Vulture pentosidine-based age estimates appear to correspond to plumage-based age estimates. Pentosidine-based age estimates for 88% of the known-aged parakeets (n = 17) were within 6 months of actual ages. Even though known ages were not available for all birds, we found a positive trend in pentosidine versus age for both species. We suggest that 6-mm diameter skin samples from the patagium of living vultures and other similar-sized birds will provide sufficient tissue for reliable age estimation and will not impair flight ability

INTERSPECIES COMPARISON OF PENTOSIDINE ACCUMULATION AND ITS CORRELATION WITH AGE IN BIRDS

Recent studies suggest that a linear correlation exists between the age of individual birds and accumulation of the advanced glycation endproduct pentosidine (Ps). We compared Ps accumulation in skin tissue of Ruffed Grouse (Bonasa umbellus) and Double-crested Cormorants (Phalacrocorax auritus). Skin samples were taken from the breasts of 52 Ruffed Grouse of known ages ranging from a few days to 10 years. Skin was cleaned of feathers and adipose tissue, acid hydrolyzed, and measured for collagen content via hydroxyproline spectrophotometric assay. Pentosidine concentrations were determined using reverse-phase high-performance liquid chromatography. Fluorescent detection (excitation: 310 nm, emission: 385 nm) revealed that concentrations of Ps per milligram of collagen increased curvilinearly with age (r2 = 0.87, P \u3c 0.0001). Additionally, a blind study of 19 Double-crested Cormorants revealed a linear relationship between Ps concentrations and age (r2 = 0.93). Comparison of these two species revealed a more rapid accumulation of Ps in Ruffed Grouse. Accurate age information could aid species recovery programs and provide insights into longevity, now understood entirely from banding programs and captive birds

Animal physiology : from genes to organisme

23a,759 p .; 30 cm