ISSN:0022-104X    

DOI:10.1002/jez.1402320302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe heterogeneous paraventricular nucleus (PVN) of birds offers favorable conditions for the analysis of intrinsic, afferent, and efferent connections of neuroendocrine systems. Paraventricular neurons are successfully impregnated with the Golgi‐technique. The findings indicate a direct influence of the cerebrospinal fluid (CSF) on the magnocellular neurons that, via their axon terminals in the neural lobe of the pituitary, are also exposed to the hemal milieu. The magnocellular neurons are intermingled with parvocellular elements which may represent local interneurons. A group of parvocellular nerve cells is identified as CSF‐contacting neurons. This type of cell forms a basic morphologic component of the avian neuroendocrine apparatus.Immunocytochemical and ultrastructural studies further support the concept of neuronal interactions between parvocellular and magnocellular elements. Moreover, these findings speak in favor of the existence of recurrent collaterals of the magnocellular neurons.Nerve cells giving rise to afferent connections to the PVN are located in the limbic system and autonomic areas of the upper and lower brainstem. Further afferents may originate from the subfornical organ, the organon vasculosum laminae terminalis, the ventral tegmentum, and the area postrema. Via efferent projections, the PVN is connected to the nucleus accumbens, lateral septum, several hypothalamic nuclei, the neural lobe of the pituitary, the organon vasculosum laminae terminalis, the subfornical organ, the pineal organ, the area postrema, the lateral habenular complex, and various autonomic areas of the reticular formation in the upper and lower brainstem and the spinal cord.In conclusion, the PVN may be regarded as an integral component of the neuroendocrine apparatus reciprocally coupled to the limbic system, several circumventricular organs, and various autonomic centers of the br

ISSN:0022-104X    

DOI:10.1002/jez.1402320303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe results obtained by topographical studies on the immunoreactive peptide systems in the embryonic and adult avian brain (domestic fowl, domestic mallard, pigeon, Japanese quail, and zebra finch) can be realized only by means of phylogenetical comparisons. The comparative studies mainly demonstrate a fascinating constancy of the immunological properties and the spatial distribution of the neuropeptides. Independent of the development of the neopallium, and the increasing cerebral complexity, the spatial distribution of the neuropeptides, the location of their main perikaryal accumulations which are interconnected by immunoreactive fiber projections (and thereby forming widespread but continuous peptide systems) remain nearly unchanged during vertebrate evolution. The recognition of the neuropeptides as integral parts of the central nervous system is demonstrated by the fact that neuropeptidergic structures connect sensory inputs with central nervous areas as well as with the peripheral endocrinium.

ISSN:0022-104X    

DOI:10.1002/jez.1402320304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe pars distalis of the avian adenohypophysis consists of well‐defined cephalic and caudal lobes which are distinct in their cellular constituents. Immunocytochemical investigations on the pituitary hormones of the pars distalis of the Japanese quail reveal five types of secretory cells, adenocorticotropin (ACTH) cells, prolactin (PRL) cells, thyroid‐stimulating hormone (TSH) cells, growth hormone GH (STH) cells, and FSH/LH (gonadotropic) cells. The ACTH cells, TSH cells, and PRL cells are restricted to the cephalic lobe, and GH (STH) cells are confined to the caudal lobe, while FSH/LH cells are distributed throughout the cephalic and caudal lobes.The median eminence of birds has distinct anterior and posterior divisions, each with different neuronal components. The avian hypophysial portal vessels also consists of two groups, anterior and posterior. The peculiar arrangement and distribution of the avian hypophysial portal vessels are possibly related to the distribution of neuropeptides in the two divisions of the median eminence and to the cytological and functional differentiation of two lobes of the pars distalis.The localization of perikarya and fibers containing luteinizing hormone releasing hormone (LHRH), somatostatin, vasotocin, mesotocin, corticotropin‐releasing factor (CRF), vasoactive intestinal polypeptide (VIP), glucagon, metenkephalin, and substance P in the hypothalamus and median eminence of the Japanese quail has been investigated by means of immunohistochemistry using antisera against the respective neuropeptides. LHRH‐, somatostatin‐, VIP‐, met‐enkephalin‐, and substance P‐immunoreactive fibers are localized in the external layer of the anterior and posterior divisions of the median eminence, while CRF‐ and vasotocin‐reactive fibers are demonstrated only in the external layer of the anterior division of the median eminence. The metenkephalin fibers are thicker in the anterior median eminence but the substance P fibers are more abundant in the posterior division. Mesotocin fibers occur only in the internal layer of the median emi

ISSN:0022-104X    

DOI:10.1002/jez.1402320305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractStudies on partially purified chicken hypothalamic luteinizing hormone releasing hormone (LHRH) utilizing chromatography, radioimmunoassay with region‐specific antisera, enzymic inactivation, and chemical modification established that the peptide is structurally different from mammalian hypothalamic LHRH. These studies demonstrated that arginine in position 8 is substituted by a neutral amino acid. On the basis of conformational criteria and evolutionary probability of amino acid interchange for arginine, the most likely substitution was glutamine. We therefore synthesized [Gln8]‐LHRH and established that it had identical chromatographic, immunologic, and biological properties to the natural chicken peptide. In concurrent studies, purification of 17 μg of an LHRH from 249,000 chicken hypothalami was achieved using acetic acid extraction, immuno‐affinity chromatography, and cation exchange and reverse phase high performance liquid chromatography. Amino acid composition and sequence analyses confirmed the structure of this form of chicken LHRH as pGlu‐His‐Trp‐Ser‐Tyr‐Gly‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402320306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractStructural requirements in LHRH for gonadotropin‐releasing activity were investigated by comparing the activity of the natural vertebrate LHRH structural variants and synthetic analogues. Substitution of Arg8results in a loss of activity of LHRH in mammals, whilst a number of amino acid substitutions for Arg8retain high gonadotropin‐releasing activity in the chicken. Thus Arg8of LHRH comprises an integral part of the binding site of LHRH and/or contributes towards the conformation of the binding site for the mammalian receptor while this does not pertain in the bird. The possibility that relative conformational stabilization of LHRH is important for biological activity in mammals but not birds, was supported by the demonstration that a γ‐lactam conformationally constrained analogue of LHRH was more active than LHRH in the mammalian system but equipotent in the bird. The chicken LHRH receptor is also relatively undiscriminating with regard to amino acid substitutions in positions 5 and 7. A series of LHRH analogues with pure antagonist activity in rats exhibited a spectrum of activities, from pure agonist to mixed activity and pure antagonist, in the chicken. These differences in LHRH structural requirements of the mammalian and avian receptor are reflected by a difference in molecular size of the chicken receptor (67,000) and mammalian receptor (60,000). Nevertheless, like the mammalian pituitary, the chicken pituitary does exhibit “desensitization” on prolonged exposu

ISSN:0022-104X    

DOI:10.1002/jez.1402320307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractAvian testicular receptors for gonadotropins show a species‐specificity similar to mammalian receptors for the binding affinity to gonadotropins of various origins. In the affinity‐capacity relationships, avian FSH receptors are classified in the same group with chelonians, that is, they exhibit relatively low affinity and high capacity. FSH receptors of the Japanese quail resemble the rat receptor with respect to the temperature‐dependence of affinity in the low‐temperature range, but also resemble reptilian or amphibian receptors with respect to binding affinities in the middle‐ to high‐temperature range. We conclude that avian gonadotropin receptors have some characteristics of homeothermic vertebrates, but still retain characteristics of poikilothe

ISSN:0022-104X    

DOI:10.1002/jez.1402320308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractIn the male chick embryo the components of the hypothalamo‐adenohypophyseal‐testicular axis initially function independenty of each other. It is not until days 12.5–13.5 that the adenohypophysis begins to regulate testosterone synthesis and secretion; on day 13.5 plasma testosterone reaches a maximum embrynic level. Thisfeed forwardregulation of the pituitary‐testicular unit appears to involve a cause and effect relation between a statistically significant increase in the number of testicular interstitial cell LH receptors on days 12.5 and 13.0 and anincrease in plasma LH levels on day 13.5 (up‐regulation). Subsequently, events occur that are interpreted as indicative of thefeedbackphase of this endocrine axis. Plasma LH levels decrease after day 13.5. Also on day 13.5 and al subsequent embryonic days, there is a significant decline in the volume density of testicular LH receptor‐positive interstitial cells (IC) associated with an internalization of the LH receptor complexes and a marked decline in plasma testosterone levels (down‐regulation). It is strongly suggested that the decline in the number of LH receptor‐positive ICs and the internalization of the LH receptor complexes in indicative of a “desensitization” of the ICs followed by a decrease in testosterone synthesis and secretion. Comparable events that occur in the female embryo with respect to the development of the hypothalamo‐adenohypophyseal‐ovarian axis are also discu

ISSN:0022-104X    

DOI:10.1002/jez.1402320309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractGrowth hormone (GH) is a protein hormone produced by the somatotrophs of the anterior pituitary gland of birds and other vertebrates. The secretion of GH in birds is under hypothalamic control; it involves three peptidergic releasing factors: growth hormone‐releasing factor (GRF) (stimulatory); thyrotropin‐releasing hormone (TRH) (stimulatory); and somatostatin (SRIF) (inhibitory). In addition, there is evidence for effects of biogenic amines (including serotonin and norepinephrine) and prostaglandins at the level of the hypothalamus and possibly also the pituitary gland. In all avian species examined, plasma concentrations of GH are high in young posthatching chicks but low in the adult and embryo. The difference in plasma concentrations of GH between young and adult birds is due to both greater GH secretion and reduced clearance. The lower secretion of GH in adult birds reflects fewer somatotrophs in the pituitary, changes in somatotroph structure, and reduced GH responses to TRH or GRF administration. There is only limited data on the role of GH in birds. GH appears to be required for normal growth; acting at least in part by increasing somatomedin production. However, plasma concentrations of GH do not necessarily correlate with growth rate. For instance, in chicks with reduced growth rate owing to either goitrogen or protein deficiency in the diet, plasma concentrations of GH are elevated. GH also can influence lipid metabolism by increasing lipolysis, decreasing lipogenesis, and stimulating the uptake of glucose by adipose tissue. The physiological significance of these actions is, however, not established. In addition, GH affects the secretion of other hormones, the immune system, and perhaps also the reproductive sys

ISSN:0022-104X    

DOI:10.1002/jez.1402320310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThis review of thyroid influence on body growth in poultry is organized around the following parameters of growth: 1) increase in body weight and skeletal size, 2) muscle growth, and 3) growth of cartilage and bone. The greatest effect of goitrogens on growth of embryos occurs during late embryogenesis at a time when normal thyroid hormone levels are increasing. Posthatching growth is reduced in severely hypothyroid animals, and body weight gain is affected more than bone growth. Thyroid hormone replacement restores body growth of thyroidectomized chickens, but supplemental hormone in normal animals has no beneficial effect on growth. Excessive T3(fed at 1 ppm) is detrimental to growth and feed efficiency. No clear correlation between thyroid hormone concentration and growth rate of normal chickens has been identified. Growth depression in sex‐linked dwarf birds is at least partially reversed by supplemental T3. Muscle growth is reduced in goitrogen‐treated chickens and the growth reduction is reversed by supplemental thyroxine. Total DNA accumulation is reduced in hypothyroid chickens, but muscle mass relative to DNA content is normal following long‐term treatment; this suggests some regulation of muscle mass relative to DNA content. T3increases the number of muscle fiber nuclei in hypothyroid chickens and the uptake of3H‐thymidine into nuclei within the basal lamina. T3directly stimulates growth and maturation of embryonic chick cartilage and enhances the in vitro action of somatomedins on cartilage growth. There is little information concerning the role of the thyroid in posthatching cartilage and bone growth in

ISSN:0022-104X    

DOI:10.1002/jez.1402320311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY