摘要:

AbstractNeuropeptides are supposed to be implicated in the regulation of hormone as well as nonhormone dependent behavioral processes in birds. Previous immunohistochemical studies have suggested that in birds opioid pentapeptides, Met‐ and Leu‐enkephalins, may be present in the brain including the regions that regulate sex hormone dependent behaviors, such as reproductive behaviors. To determine biochemically the presence of opioid peptides in the avian brain, a study was conducted to isolate these peptides from Japanese quails and zebra finches. Acetic acid extracts of the quail and finch brains were respectively forced through disposable C‐18 reversed‐phase cartridges, and then the retained material was subjected to the cation‐exchange and reversed‐phase high performance liquid chromatographic (HPLC) purifications. All of the purified substances showed a single peak on the reversed‐phase HPLC and these substances enhanced spontaneous contractions of the avian rectum. The purified bioactive substances were further subjected to amino acid sequence analysis and were characterized as peptides with the following sequences: Tyr‐Gly‐Gly‐Phe‐Met, Tyr‐Gly‐Gly‐Phe‐Leu, and Tyr‐Gly‐Gly‐Phe‐Met‐Arg‐Phe. These three peptides were identical with opioid pentapeptides, Met‐ and Leu‐enkephalins, and a heptapeptide, Met‐enkephalin‐Arg6‐Phe7, which had been previously isolated from mammalian species. This is the first direct demonstration of the presence of opioid peptides in the avian brain and confirms previous immunohistochemical findings suggesting a functional role for the opioid peptide in neural mechanisms of

ISSN:0022-104X    

DOI:10.1002/jez.1402730202

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe have recently isolated three opioid peptides, i.e., Met‐ and Leu‐enkephalins and Met‐enkephalin‐Arg6‐Phe7, from the avian brain. In the present study, therefore, effects of these endogenous opioid peptides on the electrical activity of preoptic and hypothalamic neurons of the adult male Japanese quail were examined using a brain slice preparation. All of the three opioid peptides inhibited the spontaneous firing activities of subsets of neurons in the preoptic area and the paraventricular nucleus in the hypothalamus. Threshold concentrations for the inhibitory action were between 10−7and 10−6M in Met‐ and Leu‐enkephalins and approximately 10−6M in Met‐enkephalin‐Arg6‐Phe7, respectively. In a few cells in these brain areas, however, Leu‐enkephalin rather potentiated the spontaneous activities, resulting in an increase of firing rates or a decrease of interburst intervals. The inhibitory effect of Met‐enkephalin was completely blocked by naloxone, an opioid receptor antagonist, but not affected by bicuculline, a γ‐aminobutyric acid A (GABAA) receptor antagonist. These results suggest that there are functional opiate receptors in subsets of preoptic/hypothalamic neurons and that one of their main physiological functions in these areas is an inhibition of neuronal activities. Because these brain regions are considered to be involved with the regulation of a variety of male reproductive behaviors, opioid peptides may regulate some reproductive behavior through the mechanism that provokes such an in

ISSN:0022-104X    

DOI:10.1002/jez.1402730203

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

年代:1995

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1402730204

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

年代:1995

数据来源: WILEY

摘要:

AbstractDuring gastrulation and body axis formation in medaka (Oryzias latipes) fish embryos, rhythmic contraction waves sweep across a tissue sheet known as the periderm, which covers both the developing embryo and its associated yolk cell. Cope et al. ([1990] J. Exp. Zool.,254:270–275) have found that these contractions are generated by a layer of stellate‐shaped cells which is closely apposed to the inner surface of the periderm. In this paper, we show that rhythmic contractions in the stellate cell layer are correlated with elevations of intracellular [Ca2+]. Medaka periderms were first explanted and secured to microscope coverslips using a modified plasma clot culture technique. The explants were then loaded with the calcium indicator dye Fluo‐3AM and observed with time‐lapse epifluorescence confocal microscopy. Rises of intracellular [Ca2+] were observed to propagate from cell to cell in the stellate cell layer, in the form of intercellular waves. After a latency of a few seconds, a coordinated contraction within the stellate cell layer ensued. Rhythmic Ca spikes were also observed within individual stellate cells. In many cases, rises of intracellular [Ca2+] preceded cellular contraction in these individual cells by several seconds. The Ca oscillations and Ca waves that occur in medaka stellate cells represent one of the earliest expressions of Ca‐based excitability and contractility within the blastoderm of post‐fertilization vertebrate embryos. © 1995 Wil

ISSN:0022-104X    

DOI:10.1002/jez.1402730205

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

年代:1995

数据来源: WILEY

摘要:

AbstractAs forelimb regeneration inXenopus laevisis mainly a cell proliferative event which results in a spike‐shaped appendage, we set out to examine the possibility that insulin is a growth‐promoting factor in this process. The objectives were 1) to detect the presence of insulin receptors (IRs) in the liver (a specific target organ for insulin) and IRs in the forelimb regenerates of X. laevis, 2) to determine whether the receptor is similar to IRs identified in other organisms, and 3) to absorb insulin locally by implanting anti‐insulin antibody‐soaked hydrolyzed polyacrylamide beads into regenerating forelimb outgrowths in order to assess the effects of insulin deprivation on regeneration. The results show that IRs are present inXenopusliver plasma membranes (XLPM) as well as in plasma membranes of 21 day forelimb regenerates. Insulin binding to this receptor is time‐dependent and specific, as unlabeled bovine insulin competes with radioiodinated insulin for binding to XLPM more effectively than insulin‐like growth factor‐I, guinea pig insulin, or glucagon. Scatchard analysis of insulin binding to XLPM describes a two binding site receptor possessing a low affinity (0.16 nM−1), high capacity (3.2 ± 0.9 pM/mg) binding site and a high affinity (2.7 nM−1), low capacity (0.5 ± 0.3 pM/mg) binding site. The holoreceptor has a molecular mass of 380 kDa. The reduced receptor has subunits of 130 kDa and 95 kDa. The 95 kDa subunit undergoes autophosphorylation following insulin stimulation. Implantation of hydrolyzed poly‐acrylamide beads, saturated with anti‐insulin antibody, into regenerating Xenopus Forelimbs significantly impeded development of the regenerates and, therefore, demonstrates that insulin is required for growth of Xenopus forelimb regenerates.

ISSN:0022-104X    

DOI:10.1002/jez.1402730206

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

年代:1995

数据来源: WILEY

摘要:

AbstractProduction of estradiol‐17β and cAMP was assayed during maturation of the follicle‐enclosed oocytes ofXenopus laevisandRana temporariastimulated by pituitary suspension or hCG, correspondingly. In some samples, the nuclear function was suppressed by pretreatment with AD. The level of estradiol‐17β in the oocytes of the both species was very low and was not affected by hormonal or AD treatment, while the level of cAMP (follicle + medium) increased. When maturation was stimulated by low concentrations of gonadotropic hormones inducing complete or near 100% maturation, the cAMP level increased 1.4‐ to 3.9‐fold. Both higher concentrations of the gonadotropic hormones and pretreatment of the follicles with AD increased the cAMP level still more. Combination of these treatments led to a greater increase of cAMP and to inhibition of oocyte maturation. We conclude that cAMP, rather than estradiol‐17β, is involved in the AD‐induced inhibition of amphibian oocyte maturation stimulated by gonadotropins. © 199

ISSN:0022-104X    

DOI:10.1002/jez.1402730207

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

年代:1995

数据来源: WILEY

摘要:

AbstractBacillushybridogens represent the first example of hemiclonal reproduction among invertebrates and they were analyzed in the present study for comparison with vertebrate hybridogenetic complexes (PoeciliopsisandRana). Experimental crosses of southeastern hybridogeneticB. rossius‐grandii grandiifemales with both the parental species and hybrid males were carried out to test the reproductive potential of hybridogens. Allozyme and chromosome markers indicated that hemiclonal females actually reproduced in a variety of ways. Hybridogenesis was the most common and therossiusunassorted haploset was passed to the progeny while thegrandiihaploset was discarded during meiosis and replaced by that of the fathering male. Andro‐genesis, which was much rarer, led to the production of two types of all‐paternal offspring: unipa‐rental progeny of both sexes and all‐male progeny with the same allozyme and chromosome structure as their father. Mosaics of two kinds were also produced: the “h + h” type, with two different hybridogenetic cell lines; and the “h + a” type, with one hybridogenetic and one androgenetic cell line. Mosaics evolved into intersexes when their cell lines were sexually discordant. Among the evolutionary outcomes of this wide array of reproductive ways seems to be a shift from hemiclonality to clonality. This possibility is supported by the well‐established parthenogenB. whiteiand the occasional production of rare invariant specimens from the northwestern hybridogenetic formB. rossius‐grandii benazzii. Bacillusand other unisexuals provide evidence of numerous reproductive interactions between hybrids and their bisexual relatives: the occurrence of such interactions may play an important role in the persistence, diversification and evolution of unisexuals.

ISSN:0022-104X    

DOI:10.1002/jez.1402730208

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of hypothyroidism induced by 6‐propyl‐2‐thiouracil (PTU) or thiourea (TU) on the development of the reproductive system in male and female neonatal ICR mice was investigated. PTU or TU was injected subcutaneously into experimental animals from postnatal day 1 (PD1) onward. The histological changes of the reproductive organs, formation of ovarian follicles, and spermatogenesis were examined on PD 14, 21, and 28, and the fertility of the hypothyroid mice in adulthood was followed. It was found that PTU or TU treatment did not produce an effect on the histology of the neonatal uterus and oviduct. In contrast, the drugs induced a decrease in the number of primordial follicles, multilaminar follicles, and Graafian follicles in the ovary. The number of follicles with degenerated follicular cells was increased. In the testis both PTU and TU treatments brought about a decrease in the number of seminiferous tubules with developing spermatids although the mean diameter of seminiferous tubules and the histology of the testis, epididymis, seminal vesicle, and coagulating gland was unaffected. The mating between hypothyroid females and euthyroid males and that between hypothyroid males and euthyroid females were normal with regard to the pregnancy rate, litter size, and sex ratio of offspring. The somatic growth of the resulting offspring was normal. It is concluded that the retarding effect on ovarian and testicular development in mice during neonatal period was not serious enough to adversely affect reproduction in the hypothyroid animals. © 1995 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402730209

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe Msx‐1 gene (formerly known as Hox‐7) is a member of a discrete subclass of homeobox‐containing genes. Examination of the expression pattern of Msx‐1 in murine and avian embryos suggests that this gene may be involved in the regionalization of the medio‐lateral axis during earlier development. We have examined the possible functions ofXenopusMsx‐1 during earlyXenopusembryonic development by overexpression of the Msx‐1 gene. Overexpression of Msx‐1 causes a left‐right mirror‐image duplication of primary axial structures, including notochord, neural tube, somites, suckers, and foregut. The embryonic developing heart is also mirrorimage duplicated, including looping directions and polarity. These results indicate that Msx‐1 may be involved in the mesoderm formation as well as left‐right patterning in the earlyXenopusembryonic development.

ISSN:0022-104X    

DOI:10.1002/jez.1402730210

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

年代:1995

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1402730201

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

年代:1995

数据来源: WILEY