Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 43-50).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 92-103).

Neuropeptides are central modulators of many functions including male-specific mating behaviours. Understanding how these chemical messengers modulate the neural substrates are still not well understood but remains important for biological research. In Drosophila melanogaster, two well-defined microcircuits (Longer-Mating-Duration (LMD) and Shorter-Mating-Duration (SMD)), are used to understand the underlying mechanisms of how neuropeptide interactions modulate temporal information in mating behaviours. In our study, we investigated the influence of SIFamide receptor-mediated signaling and its association to both LMD and SMD. We performed several RNAi-based screens where we identified and mapped out seven different types of neuropeptidergic neurons which were found to be important to either LMD and/or SMD. Following this analysis, we highlight three independent signaling pathways which are necessary to describe the cellular mechanics of the neuropeptides involved. Firstly, we infer that synaptic contacts between proctolin and SIFamide neurons in the subesophageal ganglion mediate inhibition in SMD whereas proctoclin as a neuropeptide modulates both LMD and SMD in a non-synaptic manner. Secondly, we describe an existing insulin-related microcircuit that is modulated by the inputs of Dimmed (DIMM), a transcription factor, through adipokinetic hormone, allatostatin A, and leucokinin to exhibit SMD. Thirdly and lastly, we discuss our interpretations of how capability neurons in the central brain resolves a potential disinhibition microcircuit in LMD via olfactory based signaling in the antennae lobe. In summary, our results contribute to establishing a model system to study neuropeptidergic microcircuits in complex mating behaviours.

No description available.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

Previous studies on the regulation of salt and water reabsorption in the insect excretory system have concentrated on the rectum, while regulation of the ileum has received little attention. Cl⁻ transport is the predominant ion transport process in both the ileum and rectum of the desert locust and drives fluid absorption. The central nervous system (CNS) was surveyed for factors which stimulate Cl⁻-dependent short-circuit current (I[formula omitted]) using in vitro flat sheet preparations of locust ileum as a bioassay. All ganglia extracts tested (except the corpora allata) caused significant increases in ileal I[formula omitted]. Extracts of muscle tissue, used as a control, had no effect on ileal I[formula omitted] indicating that stimulants were not general metabolites present in locust tissue. Crude extracts of the corpus cardiacum (CC) and fifth ventral ganglion (VG5) stimulated ileal I[formula omitted] in a dose-dependent manner and both caused an increase in K⁺ and Na⁺ absorption as previously observed with cAMP. CC and VG5 had no effect on ileal NH₄⁺ secretion but both inhibited ileal H⁺ secretion. Most of the stimulatory effects of CC and VG were largely abolished by treatment with trypsin and chymotrypsin, suggesting that the stimulants were peptides. CC and VG5 factors were apparently separate compounds because they differed in the time courses of ileal I[formula omitted] response, thermal stability, and extraction properties. Reversed-phase high performance liquid chromatography (RP-HPLC) of water extracts of CC identified two distinct factors (fractions D and F) which stimulated ileal I[formula omitted] and a third factor (fraction G) which had little effect on I[formula omitted], but which caused a five-fold increase in ileal fluid transport (J[formula omitted]). None of these fractions increased rectal J[formula omitted]; moreover, fraction D stimulated rectal I[formula omitted] at higher doses. These results provided the first indication that separate stimulants act on locust rectum and ileum. The most potent factor in CC acting on ileal I[formula omitted] was isolated using a four-step purification procedure, utilizing C₈ and phenyl RP-columns for separation. Amino acid analysis of this purified peptide indicated a molecular weight of 7700 daltons and a near complete amino acid sequence (50 out of 65) was determined. The purified factor (S. gregaria ion transport peptide; ScgITP) was assayed on all ileal ion transport processes influenced by crude CC extracts. ScgITP caused quantitatively the same range of effects as crude CC extracts, in that it stimulated Cl⁻, K⁺, and Na⁺ reabsorption and inhibited H⁺ secretion. High doses of ScgITP (5 CC equiv.ml⁻¹) caused the same maximum response on all these systems as crude CC extracts (0.25 CC equiv.ml⁻¹). ScglTP is unlikely to be chloride transport stimulating hormone, previously reported to act on the rectum, because a maximum rectal I[formula omitted] response was not achieved and there was no effect on rectal J[formula omitted], which is Cl⁻-dependent. It appears that ScgITP acts through cAMP as the second messenger to stimulate reabsorptive processes because this cyclic nucleotide mimicked the actions of ScgITP and crude CC extracts. In support of this view, ileal I[formula omitted] was also stimulated to maximum levels by 5mM theophylline and 50μM forskolin. The inhibition of H⁺ secretion by ScgITP must occur through a different intracellular pathway because this action was not mimicked by cAMP. / Science, Faculty of / Zoology, Department of / Graduate

L'omniprésence des horloges circadiennes à travers une vaste gamme de taxons démontre la valeur adaptative de connaître l'heure du jour. Ces horloges permettent aux organismes de synchroniser leurs processus biologiques quotidiens à des environnements externes et internes changeants. Dans mon projet de doctorat, j'ai utilisé la drosophile comme système modèle pour étudier les bases neurales de l'adaptation saisonnière de l'activité quotidienne par l'horloge. Chez la drosophile, l'horloge cérébrale régulant l'activité locomotrice, suivant un modèle bimodale, fonctionne comme un réseau multi-oscillateurs. Deux ensembles distincts de neurones contrôlent l'activité du matin et l’activité du soir quotidiennement. Les neurones contribuant à l'activité du soir sont nombreux (oscillateurs E : 6 LNds, 1 sLNv et environ 12 à 15 DN1ps dans chaque hémisphère) et très divers en termes de localisations anatomiques, de motifs de projection, de neurochimie et de modalités photoréceptives. Mon travail indique que les différents oscillateurs E possèdent également des activités fonctionnelles distinctes dans le réseau neuronal d'horloge. J’ai démontré que seulement 2 paires d'oscillateurs E (ITP + CRY +) sur environ 150 neurones d'horloge sont suffisantes pour l'activité d'anticipation du soir. La dissection génétique de divers sous-ensembles d'oscillateurs du soir indique que non seulement ces deux paires de neurones sont suffisantes pour l'activité du soir, mais également qu'elles sont fonctionnellement supérieures aux autres oscillateurs du soir. Par conséquent, une hiérarchie opérationnelle existe parmi les oscillateurs du soir dans lesquels les neurones oscillateurs ITP + CRY + (dorénavant, ITP E) occupent l'échelon le plus élevé. J’ai par ailleurs démontré que cette hiérarchie est plutôt flexible, et que les partenaires de cette relation hiérarchique changent de rôle en fonction des entrées neuropeptidergiques (à savoir, le PDF). Les comportement et les réponses calciques des divers neurones du soir suggèrent que le PDF et les signaux saisonniers agissent sur un cadre fonctionnel, dans lequel certains neurones construisent l'activité du soir en augmentant l’activité en fin de journée et que d'autres neurones y contribuent en inhibant l'activité du début d'après-midi. Mise à part le PDF, les indices saisonniers, tels que la durée du jour, l'intensité lumineuse et la température, déterminent la pondération fonctionnelle parmi les oscillateurs du soir. Les signaux saisonniers influencent différents oscillateurs pour remplir la même fonction sous différentes saisons. Les oscillateurs ITP E sont recrutés principalement dans des conditions hivernales, tandis que les oscillateurs non-ITP E contribuent davantage dans des conditions semblables à celles de l'été. Ce recrutement biaisé d'oscillateurs se produit en partie via la modulation des niveaux de PDF par des indices saisonniers.Même s'il existe de nombreux oscillateurs E dans le circuit neuronal circadien, leur pertinence fonctionnelle est définie par des stimuli externes (indices saisonniers) et internes (neuropeptides) grâce au recrutement de différents oscillateurs.En résumé, mon étude de doctorat tente de fournir une explication plausible sur la manière dont l'adaptation saisonnière de l'horloge circadienne est réalisée au niveau neuronal. Mes résultats supportent l'idée que le recrutement d'oscillateurs, contrôlé par l'environnement, facilite l'ajustement saisonnier sculpté par l'horloge circadienne multi-oscillateurs.LNd: dorsal-lateral neuronssLNv: small ventral-lateral neuronsDN1p: dorsal neurons 1 (posterior)ITP: Ion Transport PeptideCRY: CryptochromePDF: Pigment Dispersing Factor / The ubiquity of circadian clocks across a vast range of taxa signifies the adaptive value of knowing the time of the day. These clocks enable organisms to synchronize their daily biological processes to changing external and internal environments. In my PhD project, I used Drosophila as a model system to test hypotheses regarding the neural basis of the seasonal adaptation of the clock-driven daily activity pattern. In Drosophila, the brain clock regulating bimodal locomotor activity functions as a multi-oscillator network. Two distinct sets of neurons control morning and evening bouts of daily locomotor activity. Neurons contributing to the evening activity (E oscillators; 6 LNds, 1 sLNv and around 12 to 15 DN1ps in each hemisphere) are numerous and quite diverse within themselves in terms of their anatomical loci, projection patterns, neurochemistry, and photoreceptive modalities. My work indicates that the different E oscillators also possess distinct functional loci in the clock neuronal network. I show that only 2 pairs of E oscillators (ITP+ CRY+) out of around 150 clock neurons are sufficient for the evening anticipatory activity. Genetic dissection of various evening oscillator subsets further indicates that not only these two pairs of neurons are sufficient for the evening activity, but also, they are functionally superior to other evening oscillators in their contribution to the evening activity. Hence, an operational hierarchy exists among the evening oscillators in which the ITP+ CRY+ (henceforth, ITP E) oscillator neurons inhabit the highest rung. I further show that this hierarchy is rather flexible, and the partners of this hierarchical relationship switch roles depending on neuropeptidergic inputs (namely, PDF). Studying behavior and calcium responses in diverse evening neurons suggest that PDF and seasonal cues act on a functional framework of E neurons in which some build evening activity by promotion of activity in the later parts of the day and while others, by inhibiting activity in the earlier afternoon. Alongside PDF, seasonal cues such as day-length, light intensity and temperature, determine the functional weightage among evening oscillators. Specific seasonal cues recruit different oscillators to carry out the same function under different seasons. ITP E oscillators are recruited mostly by winter-like conditions whereas non- ITP E oscillators contribute more under summer-like conditions. This biased recruitment of oscillators partly occurs via modulation of the PDF levels by seasonal cues. Even though there are numerous E oscillators in the brain circadian circuit, their functional relevance is defined by external (seasonal cues) and internal (neuropeptides) environments through conditional oscillator recruitment. In summary, my PhD study attempts to provide a plausible explanation of how seasonal adaptation of the circadian clock and the behaviours that it times, is achieved at the neural level. My results support the idea that environmentally gated recruitment of oscillators facilitates seasonal adjustment of the daily activity pattern sculpted by the multi-oscillator circadian clock.LNd: dorsal-lateral neuronssLNv: small ventral-lateral neuronsDN1p: dorsal neurons 1 (posterior)ITP: Ion Transport PeptideCRY: CryptochromePDF: Pigment Dispersing Factor

No description available.

No description available.