The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry最新文献

{"title":"A molecular model for the evolution of endothermy in the theropod-bird lineage.","authors":"M. Schweitzer, C. Marshall","doi":"10.1002/JEZ.1132","DOIUrl":"https://doi.org/10.1002/JEZ.1132","url":null,"abstract":"Ectothermy is a primitive state; therefore, a shared common ancestor of crocodiles, dinosaurs, and birds was at some point ectothermic. Birds, the extant descendants of the dinosaurs, are endothermic. Neither the metabolic transition within this lineage nor the place the dinosaurs held along the ectothermic-endothermic continuum is defined. This paper presents a conceptual model for the evolution of endothermy in the theropod-bird lineage. It is recognized that other animals (some fish, insects, etc.) are functionally endothermic. However, endothermy in other clades is beyond the scope of this paper, and we address the onset of endothermy in only the theropod/bird clade. The model begins with simple changes in a single gene of a common ancestor, and it includes a series of concomitant physiological and morphological changes, beginning perhaps as early as the first archosaurian common ancestor of dinosaurs and crocodiles. These changes continued to accumulate within the theropod-avian lineage, were maintained and refined through selective forces, and culminated in extant birds. Metabolic convergence or homoplasy is evident in the inherent differences between the endothermy of mammals and the endothermy of extant birds. The strength and usefulness of this model lie in the phylogenetic, genetic, evolutionary, and adaptive plausibility of each of the suggested developmental steps toward endothermy. The model, although conceptual in nature, relies on an extensive knowledge base developed by numerous workers in each of these areas. In addition, the model integrates known genetic, metabolic, and developmental aspects of extant taxa that phylogenetically bracket theropod dinosaurs for comparison with information derived from the fossil record of related extinct taxa.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"10 1","pages":"317-38"},"PeriodicalIF":0.0,"publicationDate":"2001-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85864260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contribution of domestic animals to the identification of new genes involved in sex determination.","authors":"E. Pailhoux, B. Vigier, Daniel Vaiman, L. Schibler, A. Vaiman, E. Cribiu, C. Nezer, M. Georges, J. Sundström, L. Pelliniemi, M. Fellous, C. Cotinot","doi":"10.1002/JEZ.1120","DOIUrl":"https://doi.org/10.1002/JEZ.1120","url":null,"abstract":"Among farm animals, two species present an intersex condition at a relatively high frequency: pig and goat. Both are known to contain XX sex-reversed individuals which are genetically female but with a true hermaphrodite or male phenotype. It has been clearly demonstrated that the SRY gene is not involved in these phenotypes. Consequently, autosomal or X-linked mutations in the sex-determining pathway may explain these sex-reversed phenotypes. A mutation referred to as \"polled\" has been characterized in goats by the suppression of horn formation and abnormal sexual differentiation. The Polled Intersex Syndrome locus (PIS) was initially located in the distal region of goat chromosome 1. The homologous human region has been precisely identified as an HSA 3q23 DNA segment containing the Blepharophimosis Ptosis Epicanthus locus (BPES), a syndrome combining Premature Ovarian Failure (POF) and an excess of epidermis of the eyelids. In order to isolate genes involved in pig intersexuality, a similar genetic approach was attempted in pigs using genome scanning of resource families. Genetic analyses suggest that pig intersexuality is controlled multigenically. Parallel to this work, gonads of fetal intersex animals have been studied during development by light and electron microscopy. The development of testicular tissue and reduction of germ cell number by apoptosis, which simultaneously occurs as soon as 50 days post coïtum, also suggests that several separate genes could be involved in pig intersexuality.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"112 1","pages":"700-8"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72980998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Expression of P450(arom) in Malaclemys terrapin and Chelydra serpentina: a tale of two sites.","authors":"A. Place, J. Lang, S. Gavasso, P. Jeyasuria","doi":"10.1002/JEZ.1118","DOIUrl":"https://doi.org/10.1002/JEZ.1118","url":null,"abstract":"The formation of estrogens from androgens in all vertebrates is catalyzed by the \"aromatase\" complex, which consists of a membrane bound P(450) enzyme, P(450) aromatase (which binds the androgen substrate and inserts an oxygen into the molecule), and a flavoprotein (NADPH-cytochrome P450 reductase). Among vertebrates, the two major sites of aromatase expression are the brain and gonads. Given the importance of estrogen in reptile sex determination, we set out to examine whether P450arom was involved in the initiation and/or stabilization of sex determination in turtles. We examined the expression of aromatase activity in the brain and gonads of two turtle species exhibiting temperature dependent sex determination (TSD), the diamondback terrapin (Malaclemys terrapin), and the common snapping turtle (Chelydra serpentina). Estradiol when applied at stage 14 of the terrapin induces expression of aromatase in the gonad of embryos incubated at male temperatures (26.5 degrees C). The level of expression is similar to that of a normal embryonic ovary. When applied at stage 22, estradiol does not induce aromatase expression in the terrapin. The xenoestrogen, nonylphenol, sex reverses terrapin embryos at 26.5 degrees C. Letrazole, a nonsteroidal aromatase inhibitor, suppresses aromatase activity in the brain at either incubation temperature. Ovotestes are produced by letrazole administration in the terrapin when incubated at 30.5 degrees C. In the snapping turtle at stage 23, gonadal and brain aromatase activity in embryos incubated at female temperatures (30.5 degrees C) is nearly half that exhibited in terrapin embryos at the same temperature. Moreover, letrazole administration suppresses aromatase expression to nearly basal levels. At male incubation temperatures (26.5 degrees ), brain aromatase expression is nearly three times higher than at female temperatures, while gonadal expression levels are nearly one third lower. However, the gonadal expression levels at male temperatures in the snapping turtle are nearly 25 times higher than that found in the terrapin. Estradiol administration elevates this level nearly three fold. These data suggest that is not merely the expression of aromatase that is important for ovarian development, but that the level of expression may be more important.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"82 1","pages":"673-90"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73387751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sex reversal and aromatase in chicken.","authors":"Séverine Vaillant, M. Dorizzi, C. Pieau, N. Richard-Mercier","doi":"10.1002/JEZ.1123","DOIUrl":"https://doi.org/10.1002/JEZ.1123","url":null,"abstract":"Aromatase inhibitors administered before sexual differentiation of the gonads can induce sex reversal in female chickens. To analyze the process of sex reversal, we have followed for several months the changes induced by Fadrozole, a nonsteroidal aromatase inhibitor, in gonadal aromatase activity and in morphology and structure of the female genital system. Fadrozole was injected into eggs on day four of incubation, and its effects were examined during the embryonic development and for eight months after hatching. In control females, aromatase activity in the right and the left gonad was high in the middle third of embryonic development, and then decreased up to hatching. After hatching, aromatase activity increased in the left ovary, in particular during folliculogenesis, whereas in the right regressing gonad, it continued to decrease to reach testicular levels at one month. In treated females, masculinization of the genital system was characterized by the maintenance of the right gonad and its differentiation into a testis, and by the differentiation of the left gonad into an ovotestis or a testis; however, in all individuals, the left Müllerian duct and the posterior part of the right Müllerian duct were maintained. In testes and ovotestes, aromatase activity was lower than in gonads of control females (except in the right gonad as of one month after hatching) but remained higher than in testes of control and treated males. Moreover, in ovotestes, aromatase activity was higher in parts displaying follicles than in parts devoid of follicles. The main structural changes in the gonads during sex reversal were partial (in ovotestes) or complete (in testes) degeneration of the cortex in the left gonad, and formation of an albuginea and differentiation of testicular cords/tubes in the two gonads. Testicular cords/tubes transdifferentiated from ovarian medullary cords and lacunae whose epithelium thickened and became Sertolian. Transdifferentiation occurred all along embryonic and postnatal development; thus, new testicular cords/tubes were continuously formed while others degenerated. The sex reversed gonads were also characterized by an abundant fibrous interstitial tissue and abnormal medullary condensations of lymphoid-like cells; in the persisting testicular cords/tubes, spermatogenesis was delayed and impaired. Related to aromatase activity, persistence of too high levels of estrogens can explain the presence of oviducts, gonadal abnormalities and infertility in sex reversed females.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"44 1","pages":"727-40"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84751624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface glycoproteins bearing alpha-GalNAc terminated chains accompany pyriform cell differentiation in lizards.","authors":"R. Uliano, L. Ricchiari, M. Prisco, P. Andreuccetti","doi":"10.1002/JEZ.1127","DOIUrl":"https://doi.org/10.1002/JEZ.1127","url":null,"abstract":"The present investigation demonstrates that in squamate reptiles, as already reported for Podarcis sicula (Andreuccetti et al., 2001), the differentiation of pyriform cells from small, stem follicle cells is characterized by the progressive appearance on the cell surface of glycoproteins bearing alpha-GalNAc terminated O-linked side chains. Using a lectin panel (WGA, GSI-A4, GSI-B4, PSA UEA-I, PNA, Con-A, DBA, LCA, BPA, SBA), we demonstrated that, during previtellogenesis, the pattern of distribution of DBA binding sites over the follicular epithelium dramatically changes. In fact, binding sites first appear in follicular epithelium at the time that small cells begin to differentiate; in such follicles, labeling is evident on the cell surfaces of small and intermediate cells. Later on, as the differentiation progresses, the binding sites also become evident on the cell surface of pyriform cells. Once differentiated, the pattern of the distribution of DBA binding sites over the follicular epithelium does not change. By contrast, during the phase of intermediate and pyriform cell regression, DBA binding sites gradually decrease, so that the monolayered follicular epithelium of vitellogenic follicles, constituted only by small cells, shows no binding sites for DBA. It is noteworthy that binding sites for DBA are present on small cells located in contact with the oocyte membrane, but not on those located under the basal lamina or among pyriform cells, and therefore not engaged in the differentiation into pyriform cells. This finding demonstrates that, in squamates, the pattern of distribution of alpha-N-GalNAc containing glycoproteins significantly changes during previtellogenesis, and that these modifications are probably related to the differentiation of small stem cells into highly specialized pyriforms.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"1 1","pages":"769-76"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72732183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sex determination in the chicken embryo.","authors":"C. A. Smith, A. Sinclair","doi":"10.1002/JEZ.1119","DOIUrl":"https://doi.org/10.1002/JEZ.1119","url":null,"abstract":"The chicken embryo represents a suitable model for studying vertebrate sex determination and gonadal sex differentiation. While the basic mechanism of sex determination in birds is still unknown, gonadal morphogenesis is very similar to that in mammals, and most of the genes implicated in mammalian sex determination have avian homologues. However, in the chicken embryo, these genes show some interesting differences in structure or expression patterns to their mammalian counterparts, broadening our understanding of their functions. The novel candidate testis-determining gene in mammals, DMRT1, is also present in the chicken, and is expressed specifically in the embryonic gonads. In chicken embryos, DMRT1 is more highly expressed in the gonads and Müllerian ducts of male embryos than in those of females. Meanwhile, expression of the orphan nuclear receptor, Steroidogenic Factor 1 (SF1) is up-regulated during ovarian differentiation in the chicken embryo. This contrasts with the expression pattern of SF1 in mouse embryos, in which expression is down-regulated during female differentiation. Another orphan receptor initially implicated in mammalian sex determination, DAX1, is poorly conserved in the chicken. A chicken DAX1 homologue isolated from a urogenital ridge library lacked the unusual DNA-binding motif seen in mammals. Chicken DAX1 is autosomal, and is expressed in the embryonic gonads, showing somewhat higher expression in female compared to male gonads, as in mammals. However, expression is not down-regulated at the onset of testicular differentiation in chicken embryos, as occurs in mice. These comparative data shed light on vertebrate sex determination in general.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"6 1","pages":"691-9"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75225886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of duplicated zebrafish cyp19 genes.","authors":"E. F. Chiang, Y. Yan, S. Tong, P. Hsiao, Y. Guiguen, J. Postlethwait, B. Chung","doi":"10.1002/JEZ.1121","DOIUrl":"https://doi.org/10.1002/JEZ.1121","url":null,"abstract":"The zebrafish has recently been developed as a good genetic model system. We report here the use of zebrafish to study the regulation of estrogen biosynthesis. The CYP19 gene encodes cytochrome P450 aromatase, which catalyzes the synthesis of estrogens. Two cyp19 genes, termed cyp19a and cyp19b, have been isolated from zebrafish. Sequence comparison shows that Cyp19a and Cyp19b belong to two separate Cyp19 subfamilies. The cyp19a gene is expressed in the ovary, whereas cyp19b is expressed in the brain. The cyp19a and cyp19b genes are located on zebrafish chromosomes LG 18 and 25, respectively. Our data indicate that these gene loci arose through an ancient chromosomal duplication event. The expression of duplicated genes in distinct tissues may have evolutionary significance.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"105 1","pages":"709-14"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80718240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Muscle receptor organs do not mediate load compensation during body roll and defense response extensions in the crayfish Cherax destructor.","authors":"B. Patullo, Z. Faulkes, D. Macmillan","doi":"10.1002/JEZ.1129","DOIUrl":"https://doi.org/10.1002/JEZ.1129","url":null,"abstract":"It has been proposed that the abdominal muscle receptor organ (MRO) of decapod crustaceans acts in a sensory feedback loop to compensate for external load. There is not yet unequivocal evidence of MRO activity during slow abdominal extension in intact animals, however. This raises the possibility that MRO involvement in load compensation is context-dependent. We recorded from MRO tonic stretch receptors (SRs) in freely behaving crayfish (Cherax destructor) during abdominal extension occurring during two different behaviors: body roll and the defense response. Abdominal extensions are similar in many respects in both behaviors, although defense response extensions are more rapid. In both situations, SR activity typically ceased when the abdominal extension commenced, even if the joint of the SR being monitored was mechanically prevented from extending by a block. Since extensor motor neuron activity increased when the abdomen was prevented from extending, we concluded that the load compensation occurring in these behaviors was not mediated by the MROs.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"13 1","pages":"783-90"},"PeriodicalIF":0.0,"publicationDate":"2001-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86045093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sex determining genes and sexual differentiation in a marsupial.","authors":"A. Pask, M. Renfree","doi":"10.1002/JEZ.1109","DOIUrl":"https://doi.org/10.1002/JEZ.1109","url":null,"abstract":"The role of genes in the differentiation of the testis and ovary has been extensively studied in the human and the mouse. Despite over a decade of investigations, the precise roles of genes and their interactions in the pathway of sex determination are still unclear. We have chosen to take a comparative look at sex determination and differentiation to gain insights into the evolution and the conserved functions of these genes. To achieve this, we have examined a wide variety of eutherian sex determining genes in a marsupial, the tammar wallaby, to determine which genes have a conserved and fundamental mammalian sex determining role. These investigations have provided many unique insights. Here, we review the recent molecular and endocrine investigations into sexual development in marsupials, and highlight how these studies have shed light on the roles of genes and hormones in mammalian sex determination and differentiation.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"84 1","pages":"586-96"},"PeriodicalIF":0.0,"publicationDate":"2001-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78832941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sex, genes, and heat: triggers of diversity.","authors":"P. Western, A. Sinclair","doi":"10.1002/JEZ.1113","DOIUrl":"https://doi.org/10.1002/JEZ.1113","url":null,"abstract":"In vertebrates, sex is determined by a surprising variety of mechanisms. In many reptiles, the primary testis or ovary-determining trigger is regulated by egg incubation temperature. This temperature dependent sex determining (TSD) mechanism occurs in all crocodilians and marine turtles examined to date and is common in terrestrial turtles and viviparous lizards (Ewert et al. 1994. J Exp Zool 270:3-15; Lang and Andrews. 1994. J Exp Biol 270:28-44; Mrosovsky. 1994. J Exp Zool 270:16-27; Pieau. 1996. Bioessays 18:19-26; Viets et al. 1994. J Exp Zool 270:45-56; Wibbels et al. 1998. J Exp Zool 281:409-416). In contrast, sex in mammals and birds is determined chromosomally (CSD). Despite these differences, morphological development of the gonads in all these vertebrate groups appears to have been conserved through evolution. Therefore, the genetic mechanisms triggering sex determination appear not to have been conserved through evolution, although the basic genetic pathway controlling the morphological differentiation of the gonads appears to have been conserved.","PeriodicalId":77637,"journal":{"name":"The Journal of experimental zoology. Supplement : published under auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry","volume":"21 1","pages":"624-31"},"PeriodicalIF":0.0,"publicationDate":"2001-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75183906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}