Cloning and expression analysis of androgen receptor gene in chicken embryogenesis

We cloned a full-length androgen receptor (AR) cDNA from chicken (Gallus gallus) gonads. The cDNA sequence has an open reading frame of 2109 bp encoding 703 amino acids. The chicken AR (cAR) shares high homology with ARs from other species in its amino acid sequences, in particular DNA binding domain (DBD) and ligand binding domain (LBD). RT-PCR analysis revealed that cAR mRNA is expressed in several embryonic tissues of both sexes, and relatively higher expression was observed in left ovary compared with testis. The immunoreactive signal of AR was co-localized within the ovarian cell nucleus, while such nuclear localization was not detected in those of testis. To get insight on the possible role of androgen-AR signaling during gonadal development, non-steroidal AR antagonist, flutamide, was administrated in ovo. The treatment induced the disorganization of sex cords in ovarian cortex at day 12 of incubation. The effect was restored by testosterone co-treatment, implying the possibility that AR mediated signaling may be involved in ovarian morphogenesis. Furthermore, co-treatment of flutamide with estradiol-17beta (E2) also restored the phenotype, suggesting androgen-AR signaling might activate aromatase expression that is necessary for estrogen synthesis. These findings suggest androgen-AR signaling might contribute to chicken embryonic ovarian development.     

Neurochemical organization of the brain reinforcing systems

Modern concepts of neurophysiological mechanisms of the brain reinforcing systems are reviewed from A.A. Ukhtomsky's concept of dominanta. The brain mesocorticolimbic system was shown to play a key role in functioning of the brain reinforcing systems. Morphological and neurochemical organisation of this system determining the emotional sphere, was studied. The dopamine system was found to be the main neurochemical tool of the mesocorticolimbic system. Other transmitters, neuromodulators, and hormones play a regulatory role in the latter. The data obtained corroborate the authors' concept of fluctuating emotional gradient.     

Subcortical structures of the brain and the behavior of white rats

Conditioned food and defensive reflexes have been studied in white rats following bilateral injury of paleo-, archi-, neostriatum, substantia nigra and paleocortex. It has been shown that these deep structures play a role in the operational memory of animals.     

The role of vitamin A in the formation of extracellular structures of the chicken glandular stomach

Main notions on the vitamin A function in the organism are considered. A new concept is formulated postulating the vitamin A role in the support of the structure and function of the Golgi complex of epithelial cells of glandular stomach mucosa of chickens.     

Isochore structures in the chicken genome

The availability of the complete chicken genome sequence provides an unprecedented opportunity to study the global genome organization at the sequence level. Delineating compositionally homogeneous G + C domains in DNA sequences can provide much insight into the understanding of the organization and biological functions of the chicken genome. A new segmentation algorithm, which is simple and fast, has been proposed to partition a given genome or DNA sequence into compositionally distinct domains. By applying the new segmentation algorithm to the draft chicken genome sequence, the mosaic organization of the chicken genome can be confirmed at the sequence level. It is shown herein that the chicken genome is also characterized by a mosaic structure of isochores, long DNA segments that are fairly homogeneous in the G + C content. Consequently, 25 isochores longer than 2 Mb (megabases) have been identified in the chicken genome. These isochores have a fairly homogeneous G + C content and often correspond to meaningful biological units. With the aid of the technique of cumulative GC profile, we proposed an intuitive picture to display the distribution of segmentation points. The relationships between G + C content and the distributions of genes (CpG islands, and other genomic elements) were analyzed in a perceivable manner. The cumulative GC profile, equipped with the new segmentation algorithm, would be an appropriate starting point for analyzing the isochore structures of higher eukaryotic genomes.     

Chemical analysis of the developmental pattern of polysialylation in chicken brain. Expression of only an extended form of polysialyl chains during embryogenesis and the presence of disialyl residues in both embryonic and adult chicken brains

Recent studies have demonstrated the involvement of two polysialyltransferases in neural cell adhesion molecule (N-CAM) polysialylation. The availability of cDNAs encoding these enzymes facilitated studies on polysialylation of N-CAM. However, there is a dearth of detailed structural information on the degree of polymerization (DP), DP ranges, and the influence of embryogenesis on the DP. It is also unclear how many polysialic acid (polySia) chains are attached to a single core N-glycan. In this paper we applied new, efficient, and sensitive high pressure liquid chromatography methods to qualitatively and quantitatively analyze the polySia structures expressed on embryonic and adult chicken brain N-CAM. Our studies resulted in the following new findings. 1) The DP of the polySia chains was invariably 40-50 throughout developmental stages from embryonic day 5 to 21 after fertilization. In contrast, glycopeptides containing polySia with shorter DPs, ranging from 15 to 35, were isolated from adult brain. 2) Chemical evidence showed glycan chains abundant in Neu5Acalpha2,8Neu5Ac were expressed during all developmental stages including adult. 3) Levels of both di- and polySia were found to show distinctive changes during embryonic development.     

The expression pattern of opticin during chicken embryogenesis

We isolated the chicken homologue of opticin (cOptc), a member of the small leucine-rich repeat protein (SLRP) family. cOptc is expressed in the brain and the neural tube from stage 9 onward. At later stages, cOptc is expressed in the ciliary epithelium of the eye, optic stalk, Rathke's pouch, pharyngeal pouches, nasal pit and otic vesicle.     

Galanin-like immunoreactivity in the chicken brain

The anatomical distribution of neurons containing galanin has been studied in the central nervous system of the chicken by means of immunocytochemistry using antisera against rat galanin. Major populations of immunostained perikarya were detected in several brain areas. The majority of galanin-immunoreactive cell bodies was present in the hypothalamus and in the caudal brainstem. Extensive groups of labeled perikarya were found in the paraventricular, periventricular, dorsomedial and tuberal hypothalamic nuclei, and in the nucleus of the solitary tract in the medulla oblongata. In the telencephalon, immunoreactive perikarya were observed in the preoptic area, in the lateral septal nucleus and in the hippocampus. The mesencephalon contained only a few galanin-positive perikarya located in the interpeduncular nucleus. Immunoreactive nerve fibers of varying density were detected in all subdivisions of the brain. Dense accumulations of galanin-positive fibers were seen in the preoptic area, periventricular region of the diencephalon, the ventral hypothalamus, the median eminence, the central gray of the brainstem, and the dorsomedial caudal medulla. The distributional pattern of galanin-immunoreactive neurons suggests a possible involvement of a galanin-like peptide in several neuroregulatory mechanisms.     

Development and metabolism of chicken embryos in the embryogenesis under acoustic stimulation

Acoustic influence on the metabolic process in the last days of incubation of embryos of domestic chicken was found. It was shown that the changes that appear under the influence of acoustic signals lead to a decrease in incubation time. As a result of acoustic hyperstimulation, gaseous exchange and growth of the embryo continue to follow a power dependence characteristic of an earlier period of embryogenesis, i.e., the depression typical of these processes in the end of incubation is arrested. In acoustically stimulated embryos, a tendency toward a decrease in the total energy expenses on growth and metabolism is observed in the period from 17 days of incubation up to hatching, but the daily expenses on energetic exchange and growth are higher under acoustic influence than in the control group.     

Neurochemical studies on imprinting behavior in chick and duckling

The effect of lesiens in the parts of medial hyperstriatum ventrale (MHV) or lateral neostriatum (LN) on impriting behavior was examined. Bilateral lesions in MHV severely impaired imprinting behavior in ducklings, but lesions in LN did not impair such behavior. On the other hand, the birds lesioned in MHV still had brightness discriminative learning ability with perfect performance of visuomotor coordination. The neurotransmitter candidates controlling imprinting behavior in MHV were investigated using blockers of neurotransmission. 6-Hydroxydopamine (6-OHDA) and haloperidole injected into MHV did not have specific effect on imprinting behavior although catecholamine contents in MHV was clearly decreased and locomotor activity was strongly suppressed. Atropine injection into MHV caused significant impairment of following behavior, but locomotor activity was not affected. The injection of atropine into other region did not have any effect. -Bungarotoxin showed no effect on either imprinting or locomotor activity. Kainic acid injection into MHV caused the decrease of glutamate content in the MHV region and it reached maximum at 24 hours after injection. However, imprinting behavior was already impaired at 3 hours after injection, but at 24 hours it had been recovered. A same effect was observed by glutamate injection. The effect of protein synthesis inhibitor on the aquisition process of imprinting was investigated. The aquisition of imprinting was significantly impaired by cycloheximide (CHX) injection into MHV within 2 hours after the first exposure to the imprinting stimulus. When CHX was given 24 hours after, imprinting behavior was not affected.     

Clarifying tetrapod embryogenesis by a dorso-ventral analysis of the tissue flows during early stages of chicken development

The formation of an animal body remains largely a mystery. It is still not clear whether anything like an organization plan or an "archetype" as coined by Darwin himself, actually exists, or whether animals are organized by a succession of stop-and-go genetic, non-linear, instructions with no global pattern. Nevertheless, it was recognized long ago that the early stages of amniote development consist of large scale rotatory movements over a discoidal blastula (Wetzel, 1924). Such rotatory movements reshuffle a mass inside a finite volume, and thus may have to bear physical conservation laws which contribute to establish the plan of animals in a global fashion. In this article I use dual dorso-ventral imaging of the chicken blastula, to show experimentally that the global movement of early vertebrate embryogenesis is organized with a very simple topology, around and away of a series of hyperbolic points in the vector flow of movement. At the first hyperbolic point, a layer of tissue (the mesoderm) ingresses and moves as a viscous sheet radially. It is found that the sheet flows away with a scaling law for the radius R(t)～exp(t/τ). Also, the movement of this mesoderm changes the flow on the other layer (the ectoderm) by the principle of action and reaction. By mesoderm wetting the ectoderm, the first hyperbolic point migrates from the anal region, to the umbilical region. The final location of the hyperbolic point defines eventually the central part of the body (the umbilical region). Thus, the formation of the vertebrate body is fixed, as a global movement, by the dynamics of singular points in the visco-elastic flow, governed by mechanical forces within the tissue.