Post-hatching Changes Research Articles

Determination of testicular estrogen receptor alpha expression of male chickens (Gallus domesticus) with age.

Background and Aim:Estrogen activity, a central component of reproductive growth, is regulated by the receptor proteins, estrogen receptor alpha (ERα), and ER beta (ERβ) in chickens as in many other species. ERα expresses predominantly in gonads. Although the expression of ERα in embryonic gonads has been studied in detail, the expression of ERα in post-hatching male gonads has not been studied adequately. Therefore, the current research was conducted to determine the post-hatching changes in the expression of ERα in the left gonads of male chickens with age.Materials and Methods:Shaver Brown male chickens were raised and cared for according to the management guide and sacrificed at the intervals of 1, 4, and 8 weeks of age. The total RNA was extracted from the left gonads using the Trizol method and reverse transcribed using a pair of gene-specific primers. Following polymerase chain reaction amplification, the expression of ERα was quantified relative to the expression of the reference gene GAPDH.Results:The results showed that ERα expression significantly increases with age at p=0.0032. However, the increment of ERα expression from week 1 to week 4 was 2.04-fold and from week 4 to week 8 was 1.39-fold, with the later age reflecting a diminishing pattern in the increment.Conclusion:These results differentiate the post-hatching ERα expression of the left gonads of male chickens increase with age but with a diminishing gradient that may support their reproductive functions in later stages of life.

Ontogenetic Shape Change in the Chicken Brain: Implications for Paleontology.

Paleontologists have investigated brain morphology of extinct birds with little information on post-hatching changes in avian brain morphology. Without the knowledge of ontogenesis, assessing brain morphology in fossil taxa could lead to misinterpretation of the phylogeny or neurosensory development of extinct species. Hence, it is imperative to determine how avian brain morphology changes during post-hatching growth. In this study, chicken brain shape was compared at various developmental stages using three-dimensional (3D) geometric morphometric analysis and the growth rate of brain regions was evaluated to explore post-hatching morphological changes. Microscopic MRI (μMRI) was used to acquire in vivo data from living and post-mortem chicken brains. The telencephalon rotates caudoventrally during growth. This change in shape leads to a relative caudodorsal rotation of the cerebellum and myelencephalon. In addition, all brain regions elongate rostrocaudally and this leads to a more slender brain shape. The growth rates of each brain region were constant and the slopes from the growth formula were parallel. The dominant pattern of ontogenetic shape change corresponded with interspecific shape changes due to increasing brain size. That is, the interspecific and ontogenetic changes in brain shape due to increased size have similar patterns. Although the shape of the brain and each brain region changed considerably, the volume ratio of each brain region did not change. This suggests that the brain can change its shape after completing functional differentiation of the brain regions. Moreover, these results show that consideration of ontogenetic changes in brain shape is necessary for an accurate assessment of brain morphology in paleontological studies.

Post-hatch Changes in the Immunoexpression of Desmin, Smooth Muscle Actin and Vimentin in the Testicular Capsule and Interstitial Tissue of the Japanese quail (Coturnix coturnix japonica)

The post-hatch development of immunoreactivity to desmin, smooth muscle actin (SMA) and vimentin in the testicular capsule and interstitial tissue of day-old to adult quails was described in this study. The tunica albuginea of the testicular capsule was composed mainly of myoid cells. A zonal arrangement of desmin and SMA immunostaining was observed in myoid cells of the tunica albuginea in 1- to 24-day-old quails. Immunostaining for SMA and desmin was uniform in the tunica albuginea of adult birds. Vimentin immunostaining in the testicular capsule was demonstrated in mesothelial cells, endothelial cells and fibroblasts. The interstitial tissue contained mesenchymal cells, peritubular myoid cells, Leydig cells and fibroblasts. Desmin-immunopositive mesenchymal cells were present in the interstitial tissue of 1- to 17-day-old quails. Peritubular myoid cells expressed strong desmin immunostaining in all developmental stages, while the intensity of SMA immunostaining increased with testicular maturation. Vimentin was demonstrated in Leydig cells and fibroblasts, while the peritubular myoid cells displayed strong vimentin immunostaining only in adult birds. Strong vimentin immunostaining was demonstrated in the endothelial cells of capsular and interstitial blood vessels. The tunica media of these blood vessels displayed desmin and SMA immunostaining. The results of the study have established that variability exists in the distribution and intensity of desmin, SMA and vimentin immunostaining in the testicular capsule and interstitial tissue of the post-hatch Japanese quail.

Effects of Monochromatic Light on Developmental Changes in Satellite Cell Population of Pectoral Muscle in Broilers During Early Posthatch Period

To investigate the effects of various monochromatic lights on early posthatch changes in satellite cell mitotic activity of pectoral muscle, a total of 416 newly hatched broilers were exposed to blue light (BL), green light (GL), red light (RL), and white light (WL) by light emitting diode system for 3 weeks, respectively. Both, in culture and in vivo studies showed that after hatching, the relative number of satellite cells altered in correlation. The enhancement of satellite cell mitotic activity peaked at post-hatching day (P) 3 and then declined with age concomitantly with the rise in satellite cell differentiation and reduction of satellite cell proliferation. These alterations became more obvious in GL than in RL. The data suggested that early posthatch changes in satellite cell population of broilers occurred through the two different processes, i.e., cellular generation (before P3) and cellular degeneration (after P3). GL promoted significantly the broiler satellite cells to proliferate before P3 and to differentiate after P3. In addition, the circulating insulin-like growth factor-I (IGF-I) levels were higher in GL and BL groups versus WL and RL groups at P3 and P5 indicating that IGF-I plays a central role for GL illumination promoting broiler satellite cell myogenic processes during early posthatch stages.

The effects of early post-hatching changes of imprinting object on the pattern of monocular/unihemispheric sleep of domestic chicks

The pattern of monocular/unihemispheric sleep (Mo–Un sleep) was studied behaviourally in male and female chicks after early post-hatching changes of the imprinting object. Chicks were reared with an imprinting object on day 1 post-hatching which was removed or changed on day 2. On day 1, time spent in binocular sleep (both eyes closed) was similar in male and female chicks, though the number of episodes was lower in females than in males. There was no eye-closure bias in the pattern of Mo–Un sleep (one eye shut and the other open) in chicks of both sexes. On day 2, chicks subjected to the removal of imprinting object showed less time and number of episodes of binocular sleep than control chicks and chicks subjected to changes of imprinting object. There was no eye-closure bias in control chicks whilst a significant bias for more right Mo–Un sleep was recorded in chicks after removal and changes of imprinting object of both sexes. It is suggested that the removal or changes of imprinting object would cause a decrease of binocular sleep and trigger processes associated to secondary imprinting involving the left hemisphere. The bias for more right Mo–Un sleep (right eye-closure) could be the by-product of consolidation processes of secondary imprinting memories in the left hemisphere and/or of more left eye-opening as a result of periodical awakening of right hemisphere to control the environment after a stressful condition such as the removal or change of imprinting object.

Brain growth in mallards, Pekin and Muscovy ducks (Anatidae)

Post-hatching changes in brain mass were investigated in mallards and four stocks of domesticated ducks, using growth curve analysis and allometry. The birds varied in age between hatching and 154 days. Percentage brain size at hatching in ducks varies between 22.5% and 28% which fits well into the precocial category. Brain growth shows a sigmoid course. The point of inflection is very early when compared to other organs. However, growth is slow after passing the growth rate maximum. Pekins show higher absolute brain masses than mallards. However, the growth patterns with respect to time are very similar among stocks. Strongly negative allometry is found with allometric exponents between 0.31 and 0.37 with the highest value in mallards. Allometrically, there is an increasing reduction of brain mass in Pekins when compared to mallards to about 12.5% in adults. No differences were found between mallards and either Muscovies or the Muscovy × Pekin cross. The reduction in relative brain size in domesticated animals when compared to their wild ancestors is generally attributed to a decrease in functional demands resulting from the artificial environment. Because brain growth is more conservative and less influenced by selection than body weight, we assume that this reduction is, at least in part, a result of the constancy of brain growth patterns.

Brain growth in mallards, Pekin and Muscovy ducks (Anatidae)

Post-hatching changes in brain mass were investigated in mallards and four stocks of domesticated ducks, using growth curve analysis and allometry. The birds varied in age between hatching and 154 days. Percentage brain size at hatching in ducks varies between 22.5% and 28% which fits well into the precocial category. Brain growth shows a sigmoid course. The point of inflection is very early when compared to other organs. However, growth is slow after passing the growth rate maximum. Pekins show higher absolute brain masses than mallards. However, the growth patterns with respect to time are very similar among stocks. Strongly negative allometry is found with allometric exponents between 0.31 and 0.37 with the highest value in mallards. Allometrically, there is an increasing reduction of brain mass in Pekins when compared to mallards to about 12.5% in adults. No differences were found between mallards and either Muscovies or the Muscovy × Pekin cross. The reduction in relative brain size in domesticated animals when compared to their wild ancestors is generally attributed to a decrease in functional demands resulting from the artificial environment. Because brain growth is more conservative and less influenced by selection than body weight, we assume that this reduction is, at least in part, a result of the constancy of brain growth patterns.

Trk-like proteins during the post-hatching growth of the avian bursa of Fabricius.

Neurotrophins are growth factors acting on responsive cells through membrane receptors identified as Trk tyrosine kinase proteins (A, B and C). Trks are present in the mammalian lymphoid organs, and indirect evidence suggests that they are also present in the avian bursa of Fabricius. This study was designed to analyze (a) the occurrence and localization of Trk proteins in the bursa of Fabricius; and (b) whether the post-hatching growth of the organ (from hatching to 75 days) involves cells expressing Trk proteins. We used pigeon bursae of Fabricius, and rabbit polyclonal antibodies against specific epitopes of TrkA, TrkB and TrkC. Cytokeratins and vimentin were studied in parallel with label non-lymphoid cells of the bursal follicles. Immunoreactivity (IR) for all assessed antigens was found in specific non-lymphoid cells. From hatching to 15 days, TrkB-like IR was found outside the follicles in cells localized beneath the follicle associated (FAE) and interfollicular (IFE) epithelium. Between 30-75 days TrkB-like IR labelled the medullary secretory dendritic cells (SDC). The density of SDC displaying IR increased up to 60 days. TrkA-like and TrkC-like IR was primarily observed in FAE and IFE, but also in the medullary reticular epithelial cells (REC) up to 15 days. The present results provide evidence of the occurrence, localization and post-hatching changes in Trk proteins in avian bursa of Fabricius. Trks were localized on non-lymphoid cells which participate in providing the adequate microenvironment for B lymphocyte maturation. Furthermore, the cell segregation in the expression of Trks suggests specific roles for their ligands in controlling the function of medullary SDC and REC, hence bursal lymphoid follicle physiology.

Posthatch Changes in Morphology and Function of the Small Intestines in Heavy- and Light-Strain Chicks

The morphology of the small intestines of heavy (Arbor Acres) and light (Lohman) chicks was determined posthatch in parallel with digestion, enzyme secretion, and passage time. Villus height and volume increased from 4 to 10 d, particularly in the jejunum and ileum. The number of enterocytes per villus increased with age, but enterocyte density was greater in jejunum than ileum. Villus volume and enterocyte density was greater in Arbor Acres than Lohman chicks from hatching and the rate of change with age was similar in both strains. Enzyme secretion to the duodenum was higher per gram of feed intake in heavy-strain birds on Day 4 after hatching but thereafter no differences were apparent. Passage time was 50% shorter in light-strain chicks on Day 4 but the difference between the strains was not significant from Day 10. No differences in fatty acid digestion were observed with age or between strains. Nitrogen digestion increased in both strains from approximately 70% on Day 4 to close to 90% on Day 14. Starch digestion was 90 to 95% from 4 to 14 d in Arbor Acres birds, but increased from approximately 80% on Day 4 in Lohman chicks to 93% on Day 14. Feed intake may determine the amount of uptake in posthatch chicks.

Maturation of glomerular size distribution profiles in domestic fowl (Gallus gallus)

Previous histological evaluations of chick kidneys indicated nephrons continue to develop from embryonic foci for up to 6 weeks after hatching. The present study was conducted using an in vivo alcian blue staining technique to quantify posthatch changes in glomerular numbers and sizes in female domestic fowl at 1, 3, 5, 9, 12, 21, and 30 weeks of age. Changes in glomerular size distributions reflect changes in the heterogeneous nephron populations of avian kidneys. Foci of embryonic tissue were observed at the periphery of renal lobules up to 12 weeks of age. Glomerular numbers increased from 69,800/kidney at 1 week to 586,000/kidney at 12 weeks, with no further significant increase up to 30 weeks (599,000/kidney). The increase in glomerular number per gram kidney weight remained constant as kidney mass increased up to 12 weeks of age, after which the number of glomeruli per gram kidney weight declined significantly as kidney size increased without further addition of new nephrons. Glomerular size distribution profiles were constructed using eleven circumference categories. The peak number of glomeruli fell within the 0.11-0.14 mm category at 1 and 3 weeks; within the 0.15-0.18 mm category at 5, 9, and 12 weeks; and within the 0.19-0.22 mm category at 21 and 30 weeks. One and 3-week-old chicks had no glomeruli within the largest (greater than or equal to 0.35 mm circumference) size categories, and 9-12-week-old birds had significantly fewer glomeruli in these categories than 21-30-week-old birds. These results demonstrate that posthatch renal maturation in domestic fowl involves the ongoing formation of new nephrons up to 12 weeks of age, with subsequent kidney growth (12-30 weeks of age) accomplished by enlargement of existing nephrons (nephron hypertrophy). The cumulative evidence indicates that nephrons destined to develop loops of Henle (mammalian-type) develop first, with shorter (reptilian-type) nephrons developing later as the kidneys enlarge.

Post-hatching Changes in Glycogen Concentration in Tissues of Fed and Unfed Snapping Turtles

Post-hatching Changes in Glycogen Concentration in Tissues of Fed and Unfed Snapping Turtles