No description available.

1. The role of the catecholamine noradrenaline (NA) was examined during fictive swimming in Xenopus laevis tadpoles. 2. The primary effects of the amine in both embryonic and larval Xenopus was to markedly decrease motor frequency whilst simultaneously reducing rostrocaudal delays during swimming. 3. The NA-mediated modulation of swimming activity in Xenopus larvae can be reversed with phentolamine, a non-selective an adrenergic receptor antagonist, suggesting that NA may be acting through either ?1 or ?2 receptors, or a combination of both. 4. Intracellular recordings made from embryo spinal motorneurones revealed that reciprocal inhibitory glycinergic potentials are enhanced by NA. This effect is most prominent in caudal regions of the spinal cord where inhibitory synaptic drive is generally weaker. 5. NA was also found to enhance glycinergic reciprocal inhibition during swimming in larval spinal cord motomeurones. 6. Intracellular recordings, under tetrodotoxin, reveal that NA enhances the occurrence of spontaneous glycinergic inhibitory post synaptic potentials arising from the terminals of inhibitory intemeurones, suggesting that the amine is acting presynaptically to enhance evoked release of glycine during swimming. 7. The effects of NA on swimming frequency and rostrocaudal delay appear to be largely mediated through an enhancement of glycinergic reciprocal inhibition as blockade of glycine receptors with strychnine weakens the ability of the amine affect these parameters of motor output. 8. The effects of NA on motor output were also examined in embryos of the amphibian Rana temporaria. Whilst NA did not obviously affect swimming activity, the amine induced a non-rhythmic pattern of motor activity. 9. The free radical gas, nitric oxide also induced a non-rhythmic pattern of motor discharge that was remarkably similar to that elicited by NA, indicating that this neural messenger may be important for motor control.

No description available.

Testosterone has been implicated in the production of courtship pheromones in various animals. It is hypothesized that testosterone also stimulates the production and/or release of any courtship pheromones in Xenopus laevis. Castrated male frogs were implanted with empty or testosterone(T)-filled Silastic capsules. The water from testosterone-treated frogs (C+ T) and castrated frogs with empty capsules (C) was pumped into a plastic Y-maze at a flow rate of 65 ml/min. A female frog placed in theY-maze was observed for a sixty minute trial period, and the movements and position of the female frog were recorded. A total of ten female frogs were put through four different combinations of water: C+T versus C water, C+T versus plain water, C versus plain water, and plain water versus plain water. Results of a paired T -test demonstrate that the female frogs preferred the water holding C+ T males over the water holding C males (p = 0.035). These preliminary results reveal that female frogs can discern the androgen status of males based solely upon water-born chemicals released by the males. This suggests that a testosterone-dependent courtship pheromone may be released by male X. laevis for the purpose of attracting females for mating.

No description available.

No description available.

Anurans rely mainly on vocalizations for mate attraction while urodeles rely mainly on pheromones. However, the presence of breeding glands suggests that anurans may also communicate with pheromones during reproduction. Previous studies have shown that male Hymenochirus sp. are able to attract females in a Y-maze, most likely through chemical means, but the source of the attractant has not been identified. By exposing female Hymenochirus sp. to choice tests in a Y -maze it was demonstrated that the breeding glands of male Hymenochirus sp. are the source of a mate-attractant pheromone. This study represents the first experimental evidence for a pheromonal function of breeding glands and further supports the idea that anurans utilize pheromones in reproduction. Evidence is also presented suggesting that the mate attraction is temperature sensitive with an upper limit around 30°C.

by Lee Tsz On. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 148-155). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgments --- p.v / Contents --- p.vi / List of figures --- p.xii / List of table --- p.xiv / Abbreviations --- p.xv / Chapter Chapter 1 --- General Introduction / Chapter 1.1. --- Growth hormone (GH) --- p.1 / Chapter 1.1.1. --- Introduction to GH --- p.1 / Chapter 1.1.2. --- Actions of GH --- p.2 / Chapter 1.1.3. --- Structure of GH --- p.3 / Chapter 1.1.4. --- The sequence of GH --- p.5 / Chapter 1.2. --- Growth hormone receptor (GHR) --- p.6 / Chapter 1.2.1 --- Introduction to GHR --- p.6 / Chapter 1.2.2. --- Structure of the extracellular domain of GHR --- p.9 / Chapter 1.2.3. --- The regulation of GHR --- p.12 / Chapter 1.2.4. --- GHR biosynthesis --- p.13 / Chapter 1.2.5. --- Tissue distribution of GHR --- p.14 / Chapter 1.3. --- Signal transduction mechanisms of GHR --- p.15 / Chapter 1.3.1. --- Dimerization of GH and GHR complex --- p.15 / Chapter 1.3.2. --- The Jak and Stat pathway --- p.18 / Chapter 1.3.3. --- The ras and other signaling pathways --- p.20 / Chapter 1.4. --- Project aim --- p.22 / Chapter Chapter 2 --- Material and Methods / Chapter 2.1. --- Preparation of ribonuclease free reagents and apparatus --- p.23 / Chapter 2.2. --- Isolation of total RNA --- p.23 / Chapter 2.3. --- Isolation of mRNA --- p.24 / Chapter 2.4. --- Spectrophotometric quantification and qualification of DNA and RNA --- p.24 / Chapter 2.5. --- First strand cDNA synthesis --- p.25 / Chapter 2.6. --- Agarose gel electrophoresis of DNA --- p.25 / Chapter 2.7. --- Formaldehyde agarose gel electrophoresis of RNA --- p.26 / Chapter 2.8. --- Vacuum transfer of DNA to a nylon membrane --- p.26 / Chapter 2.9. --- Nucleic acids purification by MicroSpin (S-200HR) columns --- p.27 / Chapter 2.10. --- DNA radioactive labeling by nick translation --- p.27 / Chapter 2.11. --- Southern blot analysis --- p.28 / Chapter 2.12. --- Autoradiography and molecular imager --- p.28 / Chapter 2.13 . --- Linearization and dephosphorylation of plasmid DNA --- p.29 / Chapter 2.14. --- Purification of DNA from agarose using QIAEX II kit --- p.29 / Chapter 2.15. --- 3'End modification of PCR amplified DNA --- p.30 / Chapter 2.16. --- Ligation of DNA fragments to linearized vector --- p.30 / Chapter 2.17. --- Preparation of Escherichia coli competent cells --- p.31 / Chapter 2.18. --- Transformation --- p.31 / Chapter 2.19. --- Mini preparation of plasmid DNA --- p.32 / Chapter 2.20. --- Maxi preparation of plasmid DNA --- p.34 / Chapter 2.21 . --- PCR sequencing --- p.35 / Chapter 2.22. --- cDNA library screening --- p.36 / Chapter 2.23. --- Preparation and sterilization of culture medium --- p.38 / Chapter 2.24. --- Preparation of frozen stock of culture cells --- p.39 / Chapter 2.25. --- Cell passage of CHO-Kl --- p.39 / Chapter 2.26. --- Counting of cells --- p.40 / Chapter 2.27. --- Proliferation assay performed on CHO-K1 cells (MTT method) --- p.40 / Chapter 2.28. --- Luciferase assay --- p.41 / Chapter 2.29. --- SDS-PAGE preparation --- p.42 / Chapter 2.30. --- SDS-PAGE analysis of proteins --- p.42 / Chapter 2.31 . --- Recombinant protein expression --- p.43 / Chapter 2.32. --- Small scale purification of recombinant proteins --- p.44 / Chapter 2.33. --- Restriction digestion of DNA --- p.45 / Chapter 2.34. --- Purification of PCR product using QIAquick PCR purification kit --- p.45 / Chapter 2.35. --- TA cloning of PCR fragment --- p.45 / Chapter 2.36. --- Transfection of plasmid into CHO-K1 cells --- p.46 / Chapter 2.37. --- Sources of hormones --- p.46 / Chapter 2.38. --- Buffer and reagents --- p.47 / Chapter Chapter 3 --- "Cloning, expression and tissue distribution of Xenopus laevis GHR" / Chapter 3.1. --- Introduction --- p.50 / Chapter 3.2. --- Materials and methods --- p.51 / Chapter 3.2.1. --- Molecular cloning of xGHR cDNA / Chapter 3.2.1.1. --- Animals and tissues --- p.51 / Chapter 3.2.1.2. --- Reverse transcribed´ؤpolymerase chain reaction (RT-PCR) --- p.51 / Chapter 3.2.1.3. --- Subcloning of PCR amplified DNA fragment --- p.53 / Chapter 3.2.1.4. --- Library screening of xGHR --- p.53 / Chapter 3.2.1.5. --- 5 'Rapid amplification of cDNA end (5' RACE) --- p.55 / Chapter 3.2.2. --- Tissue distribution of xGHR / Chapter 3.2.2.1. --- Animals and tissues --- p.56 / Chapter 3.2.2.2. --- RT-PCR and Southern blot --- p.56 / Chapter 3.2.3. --- Eukarytoic expression of xGHR and functional assay of xGHR / Chapter 3.2.3.1. --- Subcloning ofxGHR into pRc/CMV --- p.57 / Chapter 3.2.3.2. --- Expression of xGHR in CHO-K1 cell --- p.58 / Chapter 3.2.3.3. --- Proliferation assay --- p.58 / Chapter 3.3. --- Results --- p.60 / Chapter 3.3.1. --- RT-PCR of the partial fragment --- p.60 / Chapter 3.3.2. --- Library screening of xGHR cDNA library --- p.61 / Chapter 3.3.3. --- 5' RACE --- p.64 / Chapter 3.3.4. --- The full-length cDNA sequence of xGHR --- p.65 / Chapter 3.3.5. --- Tissue distribution of xGHR mRNA --- p.69 / Chapter 3.3.6. --- Functional assay of xGHR in CHO-K1 cells --- p.71 / Chapter 3.4. --- Discussion --- p.74 / Chapter Chapter 4 --- Cloning and expression of Xenopus laevis GH-A and GH-B / Chapter 4.1. --- Introduction --- p.78 / Chapter 4.2. --- Materials and Methods --- p.79 / Chapter 4.2.1. --- PCR amplification of xGH-A and xGH-B partial fragments --- p.79 / Chapter 4.2.2. --- cDNA library screening of xGH-A and xGH-B --- p.80 / Chapter 4.2.3. --- Rapid amplification of cDNA ends of xGH-B / Chapter 4.2.3.1. --- 3'RACE --- p.80 / Chapter 4.2.3.2. --- 5'RACE --- p.81 / Chapter 4.2.4. --- Expression of xGH-A and xGH-B / Chapter 4.2.4.1 --- Construction of the expression vector --- p.84 / Chapter 4.2.4.2. --- Protein expression of xGH-A and xGH-B --- p.85 / Chapter 4.2.5. --- Purification of recombinant xGH-A and xGH-B --- p.85 / Chapter 4.3. --- Results --- p.87 / Chapter 4.3.1. --- PCRof xGH-A and xGH-B partial fragment --- p.87 / Chapter 4.3.2. --- Library screening of xGH-A --- p.87 / Chapter 4.3.3. --- 5' RACE and 3' RACE of xGH-B --- p.91 / Chapter 4.3.4. --- Sequence analysis of xGH-A and xGH-B --- p.93 / Chapter 4.3.5. --- Protein expression and purification of recombinant xGH-A and xGH-B --- p.100 / Chapter 4.4. --- Discussion --- p.102 / Chapter Chapter 5 --- Molecular cloning and function expression of goldfish GHR / Chapter 5.1. --- Introduction --- p.105 / Chapter 5.2. --- Materials and methods --- p.106 / Chapter 5.2.1. --- Molecular cloning of the partial fragment of gfGHR / Chapter 5.2.1.1. --- Primer design --- p.106 / Chapter 5.2.1.2. --- Library PCR of gfGHR partial fragment --- p.108 / Chapter 5.2.2. --- Library PCR of gfGHR cDNA sequence --- p.110 / Chapter 5.2.3. --- Determination of 3' End and 5' End sequences of gfGHR cDNA --- p.112 / Chapter 5.2.4. --- Tissue distribution of gfGHR / Chapter 5.2.4.1. --- Animals and tissues --- p.115 / Chapter 5.2.4.2. --- Semi-quantitative R T-PCR --- p.115 / Chapter 5.2.5. --- Functional expression of gfGHR in CHO-K1 cell / Chapter 5.2.5.1. --- Construction of an expression vector containing gfGHR --- p.116 / Chapter 5.2.5.2. --- Functional assay of gfGHR expression on CHO-K1 cells --- p.117 / Chapter 5.2.5.3. --- Proliferation assay --- p.118 / Chapter 5.2.5.4. --- Spi luciferase assay --- p.118 / Chapter 5.3. --- Results --- p.120 / Chapter 5.3.1. --- PCR amplification of the partial sequence of gfGHR --- p.120 / Chapter 5.3.2. --- The library PCR of gfGHR cDNA sequence --- p.122 / Chapter 5.3.3. --- The sequence of gfGHR --- p.124 / Chapter 5.3.4. --- Tissue distribution of gfGHR --- p.131 / Chapter 5.3.5. --- Proliferation assay --- p.133 / Chapter 5.3.6. --- Spi luciferase assay --- p.135 / Chapter 5.4. --- Discussion --- p.137 / Chapter Chapter 6 --- General discussion and future works --- p.145 / References --- p.148 / Appendix --- p.156

Normal male dwarf African clawed frogs, Hymenochirus sp., possess bilateral, sexually dimorphic, subcutaneous breeding glands just posterior to the forelimbs. Previous studies have shown these glands release pheromones that attract conspecific females. This thesis shows the pheromones also stimulate the reproductive system of conspecific females. Females exposed to normal males prior to mating then allowed to mate with the normal males released a higher number of eggs than females who were not exposed to normal males prior to mating. Microscopic examination of ovarian tissue revealed that females exposed to normal males also produced more highly-developed oocytes than did females not exposed to normal males. These results suggest male Hymenochirus use pheromones not only to attract potential mates, but to increase female receptivity and readiness to mate. Evolutionarily, these pheromonal effects would likely benefit males by increasing their chances of breeding, increasing the number of eggs released by their mates, and thus the number of offspring in the next generation.

Differences in osmoregulatory behaviors were studied in two stream-dwelling tree frogs (Pseudacris cadaverina and P. regilla) with different natural histories. This study supports the idea that the natural history of a species has a strong effect on behavior associated with osmoregulation.