The 1980's heralded the discovery and identification of extra-pituitary sources of the neurohypophysial hormone oxytocin in non-neural tissues of several animal species. The presence, location and biosynthesis of significant amounts of oxytocin in the ovarian corpus luteum was followed by the immunocytochemical demonstration of an oxytocin-like peptide in the testicular interstitial cells. Leydig cells, which comprise up to 80% of the testicular intertubular cell population, are known to synthesize testosterone in situ. Indirect evidence indicated that an oxytocin-like peptide was also present in Leydig cells. The question arose whether this peptide was synthesized de novo by Leydig cells or was taken up and stored by the cells following biosynthesis at some other intra- and/or extra-gonadal source(s). Since luteinizing hormone (LH) and ascorbate are known to augment the production of oxytocin in ovarian granulosa cells, varying concentrations of these two stimulants were used to monitor the biosynthesis of oxytocin from isolated Leydig cells in culture. / Ph. D.

Limited information is available concerning the molecular and cellular mechanisms that regulate expression of insulin-like growth factor-I (IGF-I) and IGF-binding proteins (IGFBPs) genes in mammary epithelial cells. To test the hypothesis that IGF-I affects growth of bovine mammary epithelial cells through an autocrine and/or paracrine pathway, several cell lines were developed expressing an ovine exon-2 containing IGF-I cDNA under the control of the mouse mammary tumor virus-long terminal repeat (pMMTV-IGF-I), early simian virus (pSV40-IGF-I), and herpes simplex thymidine kinase (pTK-IGF-I) promoters. Stably transfected clones were generated by cotransfection of clonal MAC-T cells with the IGF-I expression vectors and a plasmid conferring resistance to hygromycin-B (HYG-B), using a calcium phosphate precipitation procedure. Induction of the MMTV-LTR with the glucocorticoid dexamethasone (DEX) was required for enhanced expression of IGF-I in MD-IGF-I (MD=Mammary Derived) cells, whereas SV40-IGF-I cells constitutively expressed the highest levels of IGF-I, followed by TK-IGF-I cells. Activity of the MMTV promoter in MD-IGF-I cells was coordinately regulated by lactogenic hormones and extracellular matrix. Acute secretion of DEX-induced recombinant IGF-I by MD-IGF-I cells stimulated cell proliferation through an autocrine/paracrine pathway and triggered the expression of IGFBP-3. Neither acute nor constitutive expression of IGF-I affected expression of type 1 IGF receptor mRNAs, but down-regulated cell surface receptor levels, in the order SV40-> TK- > MD-IGF-I. Secretion of IGF-I-induced IGFBP-3 potentiated the mitogenic actions of IGF-I as evidenced by enhancement of [³H]thymidine uptake into DNA of parental MAC-T cells. This study provides evidence that local production of IGF-I can stimulate cell proliferation of bovine mammary epithelial cells through an autocrine/paracrine mode of action. We suggest that secretion of IGF-I-induced IGFBP-3 by bovine mammary epithelial cells enhances cell responsiveness to IGF-I, but does not prevent down-regulation of the IGF-I receptor in cells constitutively expressing IGF-I. / Ph. D.

Thesis (PhD (Biochemistry))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The multiplication of cells proceeds through consecutive phases of growth and division (G1, S, G2 and M phases), in a process known as the cell cycle. The transition between these phases is regulated by so-called checkpoints, which are important to ensure proper functioning of the cell cycle. For instance, mutations leading to faulty regulation of the G1/S transition point are seen as one of the main causes of cancer. Traditionally, models for biological systems that show rich dynamic behavior, such as the cell cycle, are studied using dynamical systems analysis. However, using this analysis method one cannot quantify the extent of control of an individual process in the system. To understand system properties at the process level, one needs to employ methods such as metabolic control analysis (MCA). MCA was, however, developed for steady-state systems, and is thus limited to the analysis of such systems, unless the necessary extensions would be made to the framework. The central question of this thesis focuses on quantifying the control in mathematical models of the G1/S transition by the individual cell cycle processes. Since MCA was never applied to the cell cycle, several new methods needed to be added to the framework. The most important extension made it possible to follow and quantify, during a single cell cycle, the control properties of the individual system processes. Subsequently, these newly developed methods were used to determine the control by the individual processes of an important checkpoint in mammalian cells, the restriction point. The positioning of the restriction point in the cell cycle was distributed over numerous system processes, but the following processes carried most of the control: reactions involved in the interplay between retinoblastoma protein (Rb) and E2F transcription factor, reactions responsible for the synthesis of Delayed Response Genes and Cyclin D/Cdk4 in response to growth signals, the E2F dependent Cyclin E/Cdk2 synthesis reaction, as well as the reactions involved in p27 formation. In addition it was shown that these reactions exhibited their control on the restriction point via the Cyclin E/Cdk2/p27 complex. Any perturbation of the system leading to a change in the restriction point could be explained via its e ect on the Cyclin E/Cdk2/p27 complex, showing a causal relation between restriction point positioning and the concentration of the Cyclin E/Cdk2/p27 complex. Finally, we applied the new methods, with a modular approach, to compare a number of cell cycle models for Saccharomyces cerevisiae (budding yeast) and mammalian cells with respect to the existence of a mass checkpoint. Such a checkpoint ensures that cells would have a critical mass at the G1/S transition point. Indeed, in budding yeast, a correction mechanism was observed in the G1 phase, which stabilizes the size of cells at the G1/S transition point, irrespective of changes in the specific growth rate. This in contrast to the mammalian cell cycle models in which no such mass checkpoint could be observed in the G1 phase. In this thesis it is shown that by casting specific questions on the regulation and control of cell cycle transition points in the here extended framework of MCA, it is possible to derive consensus answers for subsets of mathematical models. / AFRIKAANSE OPSOMMING: Die selsiklus bestaan uit agtereenvolgende groei- en delingsiklusse wat tot selvermeerdering lei. Die siklus word gekenmerk deur onderskeie fases (G1, S, G2 en M) wat deur sogenaamde beheerpunte gereguleer word. Hierdie beheerpunte verseker dat selvermeerdering nie ongekontroleerd kan plaasvind nie en mutasies wat lei tot foutiewe regulering van die G1/S transisiepunt word as een van die hoofoorsake van kanker beskou. Die hoofdoel van hierdie studie was om die beheer wat selsiklusprosesse op die G1/S transisie uitoefen met behulp van wiskundige modelle te kwantifiseer. Omdat biologiese sisteme soos die selsiklus ryk dinamiese gedrag vertoon, word hulle tradisioneeldeur middel van dinamiese sisteemanalise bestudeer. Die analisemetode beskik egter nie oor die vermoë om die hoeveelheid beheer wat afsonderlike sisteemprosesse op 0n sisteemeienskap uitoefen te kwantifiseer nie. Om sisteemeienskappe op prosesvlak te verstaan moet metodes soos metaboliese kontrole analise (MKA) ingespan word. MKA was egter ontwikkel om sisteme in 0n bestendige toestand te analiseer en aangesien MKA nog nooit vantevore vir selsiklus analises gebruik was nie, moes nuwe MKA tegnieke gedurende die studie ontwikkel word. Die belangrikste van die metodes maak dit moontlik om beheer (soos uitgeoefen deur die onderskeie sisteemprosesse) oor 0n enkele selsiklus na te volg en te kwantifiseer. Die nuut-ontwikkelde metodes was vervolgens gebruik om te bepaal hoe een so 0n beheerpunt in soogdierselle - die restriksiepunt - deur die onderskeie sisteemprosesse beheer word. Die studie het aangedui dat die posisie van die restriksiepunt tydens die selsiklus deur ’n verskeidenheid sisteemprosesse beheer word. Die bevinding was dat vier prosesse beduidend meer beheer op die posisie van die restriksiepunt uitoefen: Reaksies wat betrekking het op die wisselwerking tussen retinoblastoma proteïen (Rb) en E2F transkripsiefaktor; reaksies verantwoordelik vir die sintese van vertraagde responsgene en Siklien D/Cdk4 in respons tot groeiseine; die E2F afhanklike Siklien E/Cdk2 sintesereaksie; sowel as die reaksies betrokke in p27 vorming. Daar was ook aangetoon dat hierdie reaksies hul beheer op die posisie van die restriksiepunt deur die Siklien E/Cdk2/p27 kompleks uitoefen, siende enige sisteemversteuringe (wat tot veranderinge in die restriksiepuntposisie aanleiding gee) deur veranderinge in die kompleks verklaar kon word - 0n observasie wat aandui dat daar 0n kousale verhouding is tussen die posisie van die restriksiepunt en die Siklien E/Cdk2/p27 kompleks. Die nuut-ontwikkelde metodes was verder gebruik om 0n verskeidenheid selsiklusmodelle van Saccharomyces cerevisiae (bakkersgis) en soogdierselle met 0n modulêre aanpak te vergelyk om te bepaal of daar 0n massa beheerpunt in beide soogdier- en bakkersgisselle bestaan. Daar word gepostuleer dat hierdie beheerpunt verseker dat selle 0n kritiese massa by die G1/S transisiepunt bereik. Die resultate van die studie dui daarop dat bakkersgis, anders as soogdierselle, oor so 0n korreksiemeganisme beskik. Die meganisme stabiliseer die grootte van selle in die G1 fase ondanks veranderinge in die groeitempo van die selle, sodat massa homeostaties by die G1/S transisiepunt gehandhaaf word. Die studie het getoon dat moeilike vrae met betrekking tot die selsiklus beantwoord kan word deur van wiskundige modelle gebruik te maak en die probleme in die nuut-ontwikkelde metaboliese kontrole analise raamwerk te giet.

It is of interest to understand how new neurons incorporate themselves into the existing circuitry of certain neuronal populations. One such population of neurons is that which are born in the subventricular zone (SVZ) and migrate to the olfactory bulb where they differentiate into granule cells. Another area of interest is the role of brain-derived neurotrophic factor (BDNF) on the survival and overall health of these neurons. This study aimed to test whether or not BDNF is a survival factor for adult-born granule cells. Here were utilized a transgenic mouse model over-expressing BDNF under the α- calcium/calmodulin-dependent protein kinase II (CAMKIIα) promoter, and tested its effect on olfactory granule cells under sensory deprived conditions. Results from this experiment indicated that there was no significant difference in cell death or cell survival when comparing transgenic and wild type animals. We concluded that BDNF is not a survival factor for adult-born granule cells. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Establishing appropriate animal models for the study of human memory is paramount to the development of memory disorder treatments. Damage to the hippocampus, a medial temporal lobe brain structure, has been implicated in the memory loss associated with Alzheimer’s disease and other dementias. In humans, the role of the hippocampus is largely defined; yet, its role in rodents is much less clear due to conflicting findings. To investigate these discrepancies, an extensive review of the rodent literature was conducted, with a focus on studies that used the Novel Object Recognition (NOR) paradigm for testing. The total amount of time the objects were explored during training and the delay imposed between training and testing seemed to determine hippocampal recruitment in rodents. Male C57BL/6J mice were implanted with bilateral dorsal CA1 guide cannulae to allow for the inactivation of the hippocampus at discrete time points in the task. The results suggest that the rodent hippocampus is crucial to the encoding, consolidation and retrieval of object memory. Next, it was determined that there is a delay-dependent involvement of the hippocampus in object memory, implying that other structures may be supporting the memory prior to the recruitment of hippocampus. In addition, when the context memory and object memory could be further dissociated, by altering the task design, the results imply a necessary role for the hippocampus in the object memory, irrespective of context. Also, making the task more perceptually demanding, by requiring the mice to perform a two-dimensional to three-dimensional association between stimuli, engaged the hippocampus. Then, in the traditional NOR task, long and short training exploration times were imposed to determine brain region activity for weak and strong object memory. The inactivation and immunohistochemistry findings imply weak object memory is perirhinal cortex dependent, while strong object memory is hippocampal-dependent. Taken together, the findings suggest that mice, like humans, process object memory on a continuum from weak to strong, recruiting the hippocampus conditionally for strong familiarity. Confirming this functional similarity between the rodent and human object memory systems could be beneficial for future studies investigating memory disorders. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Changes in synaptic strength underlie synaptic plasticity, the cellular substrate for learning and memory. Disruptions in the mechanisms that regulate synaptic strength closely link to many developmental, neurodegenerative and neurological disorders. Release site probability (PAZ) and active zone number (N) are two important presynaptic determinants of synaptic strength; yet, little is known about the processes that establish the balance between N and PAZ at any synapse. Furthermore, it is not known how PAZ and N are rebalanced during synaptic homeostasis to accomplish circuit stability. To address this knowledge gap, we adapted a neurophysiological experimental system consisting of two functionally differentiated glutamatergic motor neurons (MNs) innervating the same target. Average PAZ varied between nerve terminals, motivating us to explore benefits for high and low PAZ, respectively. We speculated that high PAZ confers high-energy efficiency. To test the hypothesis, electrophysiological and ultrastructural measurements were made. The terminal with the highest PAZ released more neurotransmitter but it did so with the least total energetic cost. An analytical model was built to further explore functional and structural aspects in optimizing energy efficiency. The model supported that energy efficiency optimization requires high PAZ. However, terminals with low PAZ were better able to sustain neurotransmitter release. We suggest that tension between energy efficiency and stamina sets PAZ and thus determines synaptic strength. To test the hypothesis that nerve terminals regulate PAZ rather than N to maintain synaptic strength, we induced sustained synaptic homeostasis at the nerve terminals. Ca2+ imaging revealed that terminals of the MN innervating only one muscle fiber utilized greater Ca2+ influx to achieve compensatory neurotransmitter release. In contrast, morphological measurements revealed that terminals of the MN inner vating multiple postsynaptic targets utilized an increase in N to achieve compensatory neurotransmitter release, but this only occurred at the terminal of the affected postsynaptic target. In conclusion, this dissertation provides several novel insights into a prominent question in neuroscience: how is synaptic strength established and maintained. The work indicates that tension exists between energy efficiency and stamina in neurotransmitter release likely influences PAZ. Furthermore, PAZ and N are rebalanced differently between terminals during synaptic homeostasis. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

A pineal participa da sincronização do organismo pela síntese de melatonina. Diabetes é um distúrbio metabólico caracterizado por hiperglicemia. Diante da controvérsia sobre a síntese de melatonina em animais diabéticos, esse trabalho objetivou avaliar as alterações da glândula pineal mediante o diabetes induzido por STZ (60mg/kg, i.p.). Ratos wistar (250-280g, 12h/12h claro/escuro) foram utilizados em todos os procedimentos que envolveram técnicas de FACS, microdiálise, HPLC, radiometria da atividade enzimática e qPCR. Os resultados mostraram que o diabetes causa diminuição (50%) e perda do perfil mono/bifásico da síntese pineal de melatonina, que não é causada por necrose ou apoptose dos pinealócitos e reflete um desarranjo no metabolismo pineal, evidenciado pela diminuição na atividade da AANAT (55%). Observou-se também um desbalanço rítmico de fatores determinantes como a expressão do receptor ß1 e a atividade e expressão das enzimas TPH1 e HIOMT. A menor concentração de melatonina circulante pode ser um fator contribuinte para o desenvolvimento da doença. / The gland is involved in the organism synchronization via its hormone melatonin. Diabetes involves hyperglicemia and insulin synthesis/signaling impairment. The aim of this work was to evaluate the pineal melatonin synthesis in STZ-diabetic rats (60mg/kg, i.p.). Male wistar rats (250-280g, 12h/12h light/dark) were used as the animal model and FACS, microdialysis, HPLC, enzyme activity assay and qPCR were the techniques used to evaluate the pineal phisiology. The results show a decrease in pineal melatonin (50%) and a circadian profile impairment that were not due to necrosis or apoptosis. This finding reflects an important impairment in the pineal metabolism that was related to a decrease in AANAT activity (55%). An alteration in the rhthmicity of important factors, such as the ß1-adrenergic receptor expression and the TPH1 and HIOMT activity and expression, was also observed. This decrease in circulating melatonin may be of fundamental importance to the establishment and maintenance of diabetes.

Thesis (M.Sc.)--Memorial University of Newfoundland, Faculty of Medicine, 1999. / Bibliography: leaves 98-114.

[Truncated abstract] This study describes the results of a four and a half year investigation examining local regulation of ion transport through pumping epithelial cells. The study focussed on the standard isolated toad skin preparation, made famous by Hans Ussing. Originally, the objective was to perform some simple manipulations on the isolated toad skin, a standard and well-tested epithelial layer, which, according to the literature, was a well-behaved and stable preparation. The purpose of doing these toad skin experiments was to gain familiarity with the experimental techniques, such as measuring the open-circuit voltage (Voc) and the short-circuit current (Isc) across an epithelium. In the process, the experimental information that was obtained was to assist in the development and refinement of a mathematical model of a single pumping epithelial cell . . . Finally, it should be emphasised the toad skin was a convenient tissue model for exploring more general issues such as: (i) how pumping epithelial cells may adjust to changes in the extracellular environment by locally regulating their membrane conductances; (2) how the topology of a cell can influence its function (i.e. the topology can determine whether a cell is optimised for salt transport or water transport). (3) how different cells, with different functions, may be positioned in apposition in a pumping epithelial tissue so that gradients generated by one cell type can be utilised by another. From a broader perspective, it is likely that such issues are also applicable to other pumping epithelia, and ultimately, may assist in understanding how these epithelia function.

A pineal participa da sincronização do organismo pela síntese de melatonina. Diabetes é um distúrbio metabólico caracterizado por hiperglicemia. Diante da controvérsia sobre a síntese de melatonina em animais diabéticos, esse trabalho objetivou avaliar as alterações da glândula pineal mediante o diabetes induzido por STZ (60mg/kg, i.p.). Ratos wistar (250-280g, 12h/12h claro/escuro) foram utilizados em todos os procedimentos que envolveram técnicas de FACS, microdiálise, HPLC, radiometria da atividade enzimática e qPCR. Os resultados mostraram que o diabetes causa diminuição (50%) e perda do perfil mono/bifásico da síntese pineal de melatonina, que não é causada por necrose ou apoptose dos pinealócitos e reflete um desarranjo no metabolismo pineal, evidenciado pela diminuição na atividade da AANAT (55%). Observou-se também um desbalanço rítmico de fatores determinantes como a expressão do receptor ß1 e a atividade e expressão das enzimas TPH1 e HIOMT. A menor concentração de melatonina circulante pode ser um fator contribuinte para o desenvolvimento da doença. / The gland is involved in the organism synchronization via its hormone melatonin. Diabetes involves hyperglicemia and insulin synthesis/signaling impairment. The aim of this work was to evaluate the pineal melatonin synthesis in STZ-diabetic rats (60mg/kg, i.p.). Male wistar rats (250-280g, 12h/12h light/dark) were used as the animal model and FACS, microdialysis, HPLC, enzyme activity assay and qPCR were the techniques used to evaluate the pineal phisiology. The results show a decrease in pineal melatonin (50%) and a circadian profile impairment that were not due to necrosis or apoptosis. This finding reflects an important impairment in the pineal metabolism that was related to a decrease in AANAT activity (55%). An alteration in the rhthmicity of important factors, such as the ß1-adrenergic receptor expression and the TPH1 and HIOMT activity and expression, was also observed. This decrease in circulating melatonin may be of fundamental importance to the establishment and maintenance of diabetes.