Plants contain a host of secondary metabolites that may be of dietary use to man. A comprehensive approach to plant-based nutrition would include investigating all aspects of a nutrient, from creation through storage and consumption. Here, experiments address each of these facets for a group of important antioxidant and pigment compounds, the carotenoids. The carotenoid biosynthetic pathway regulatory mechanisms leading to lycopene accumulation are well defined in the model fruit, tomato. Those leading to accumulation of other carotenoids and flesh colors, however, are poorly understood. The variety of flesh colors available in watermelon fruit (red, orange, salmon yellow, and canary yellow) makes it an ideal candidate for investigating the regulation of the full pathway. Carotenoid accumulation was measured in ten watermelon varieties, representing the four flesh colors and three ploidy levels, throughout fruit maturation. It was found that the putative regulatory mechanisms controlling lycopene accumulation in red-fleshed fruit may be applied in a generalized fashion to each flesh color in respect to the major carotenoid accumulated at maturity. Additionally, triploid varieties were generally found to have higher accumulation levels than diploids, and tetraploids were intermediate to both. In addition to total carotenoid content, many factors are important in determining perceived benefit. Several of these factors involve components of the food matrix, cellular and subcellular species-specific characteristics of the food which act as barriers to nutrient release. Cell size, cell wall, and chromoplast (the carotenoid storage organelle) characteristics were observed in nine fruits and vegetables using light and transmission electron microscopy. Watermelon, tomato, and melon have the largest cells. Sweet potato, butternut squash, carrot, and mango have the most fibrous cell walls; mango and papaya additionally had the thickest walls. Chromoplast globular, tubular, crystalline, and membranous substructures were described for each food. These food matrix factors may be related to differences in carotenoid bioaccessibility between food sources. An in vitro digestion experiment was used to determine carotenoid bioaccessibility for each of these foods. Per serving, grapefruit yielded the most lycopene while carrot gave the most ?-carotene, ?-carotene, lutein, and phytoene, and mango proved a good source of violaxanthin.

Thesis (M. Phil.)--University of Hong Kong, 1982.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

The procerebrum of terrestrial molluscs is an important processing centre for olfaction. While the physiology of the procerebrum is relatively well characterized, the procerebrum's structure and organization has not been previously investigated in detail. The goal of this thesis is to better characterize the structural organization of the procerebrum and to understand how it compares with other olfactory systems. / The morphology of the procerebral neurons in the snail Helix aspersa was investigated through intracellular injections of biocytin. The population of cells is heterogeneous, but no formal categorization of neuronal types was possible. The main difference among cells lies in the placement of the cells' neurites. Furthermore, contradicting previous results, certain neurons were found to have neurite projections outside the procerebrum, travelling as far as the contralateral cerebral ganglion. / To investigate if differences in sites of arborization represent functional differences, the distribution of synaptic contacts on labelled cells was studied using serial sections and electron microscopy. Neurons with different sites of arborization have distinct patterns of synapse distribution. Cells with arborizations in the procerebrum but not in the internal mass have large varicosities specialized for output. Cells that arborize in the internal mass or outside the procerebrum have mostly input synapses proximal to the soma and mostly output synapses in the terminal region of the neurites. These latter cells appear to transmit information from the procerebral cell body mass to other brain regions. The implications of these data are, firstly, that the procerebrum directly distributes processed information throughout the nervous system. Secondly, the procerebral neuron population may be divisible into two subgroups: intrinsically arborizing interneurons and projection neurons. / These results suggest a novel mechanism by which compartmentalization could be achieved in the procerebrum. Compartmentalization is believed to be important for processing olfactory information, is present in most olfactory centres but has not previously been described in the molluscan olfactory system. I propose that varicosities on the local interneurons generate foci of activity in the procerebrum which, in turn, activate specific subsets of output neurons, similar to what happens in other olfactory systems.

The morphology of C3, a motoneuron mediating the tentacle withdrawal reflex, was investigated in the snail Helix aspersa by intracellular injections of the tracers Neurobiotin and biocytin. Axonal projections were identified in the optic nerve, the olfactory nerve, the internal peritentacular nerve, the external peritentacular nerve, the cerebral-pedal connective and the cerebral commissure. A rare characteristic of the cell was the multibranching of axons in the neuropil and the exiting of this bundle of fibres into the cerebral-pedal connective. Dendritic arborizations were observed branching from the cell body, the axon hillock and the dorsal main axon. In addition, tufts of dendrites were seen to branch from the ventral axon. Based on its morphology, C3 is probably a central component in the avoidance behaviour, receiving sensory input at extensive dendritic sites and sending axons to a number of key effector sites to co-ordinate the chain of reactions that constitutes the snail's avoidance behaviour.

The crayfish, Procambarus clarkii, has a multitude of ideal sites in which synaptic transmission may be studied. Its opener muscle, being innervated by a single excitatory neuron is a good model for studying the structure/function of neuromuscular junctions since the preparation is identifiable from animal to animal and the nerve terminals are visible using a vital dye. This allows ease in finding a suitable site to record from in each preparation and offers the ability to relocate it anatomically. Marking a recorded site and rebuilding it through electron microscopy gives good detail of synaptic struture for assesment.In the first of these studies, low output sites known as stems (which lie between varicosities) were used to reduce n (number of release sites) in order to minimize synaptic complexity so individual quantal events could be analyzed by their unique parameters (area, peak, tau, rise time and latency). This was in attempt to uncover specific quantal signatures that could be traced back to the structure of the area recorded. It was found that even at stem regions synaptic structure is still complex having multiple synapses each of which could harbor a number of AZs. This gives insight as to how quantal analysis should be treated. Even low output synapses n must be treated at the AZ level.Synaptic depression was studied at the crayfish extensor muscle. By depressing the phasic neuron and recording from the muscle it appears thatdepression is a presynaptic phenomenon. The use of 5-HT gave insight to vesicular dynamics within the nerve terminal, by delaying depression and increasing maximum EPSP amplitude. TEM of phasic nerve terminals reveals no change in numbers of dock or RRP vesicles. Short term facilitation and vesicular dynamics were studied with the use of 5-HT and a neurotoxin TBOA, which blocks the glutamate transporter. In this study I showed differential mechanisms that control RRP and RP vesicles. By blocking glutamate reuptake, the RRP is depleted as shown by reduced EPSPs, but recovered with 5-HT application. The understanding of vesicle dynamics in any system has relevance for all chemical synapses.

Blue-flowered Conospermum are endemic to Western Australia, and show great potential as cut flowers. Propagation from cuttings or seed proved difficult, and root initiation in vitro is problematic. This thesis examines the floral biology of the species and the possibility of using somatic embryogenesis to overcome propagation problems. A survey of explant tissue types for C. eatoniae and C. caeruleum was carried out to identify tissue that could be induced into embryogenic pathways. Vegetative, semi-floral and floral buds were initiated into culture from February to June, but were found unsuitable for embryogenesis, producing shoots, callus or dying in culture. Leaves from in vitro leaf cultures formed callus in the presence of 2,4-D and BAP, but were unable to differentiate into embryos in the presence of a variety of growth regulator combinations and concentrations. Immature zygotes died in culture. Direct embryogenesis and/or embryogenic callus was observed on mature zygotes of the species C. caeruleum, C. spectabile, C. dorrienii and C. brownii, and somatic embryos were maintained in culture for up to 18 months for C. caeruleum. Maturation and germination of somatic embryos proved difficult; treatments of cold, ABA, desiccation or mannitol did not induce maturation. It appears that developmental pathways in Conospermum are well defined and are difficult to alter in vitro. It was concluded that somatic embryogenesis has limited commercial potential in these species. Conospermum species have an active pollination mechanism where the style is held in a state of tension when the flower opens. When pressure is applied at the base of the style by an insect, the style flicks downwards, striking the insect pollinator and releasing pollen from the anther in a single dusty mass. However, the breeding systems of blue-flowered Conospermum have not previously been well explored. Flowers on a C. eatoniae inflorescence opened from the basal end upwards acropetally, with the terminal two or three buds never opening. Fruit and seed set occurred only from the basal one to three buds. Isolation of C. eatoniae and C. amoenum flowers showed they were unable to self-pollinate in the absence of insect pollinators. Experiments to determine the timing of the peak of stigmatic receptiveness were inconclusive. Pollen germinated and penetrated the stigma 0 ¡V 6 days after anther dehiscence. Pollen loads on the stigma did not relate to the number of pollen tubes observed down the style. Controlled pollinations of cultivated C. eatoniae at a field station using self and cross pollen, revealed compatibility with a range of pollen genotypes, as pollen tubes were observed extending down the style. However, late-acting incompatibility could not be ruled out as controlled crosses failed to set any seed as flowers were shed from the bush. DNA analysis of open pollinated C. eatoniae seed progeny from two plants from a field station and two plants in natural bushland revealed very different pollination habits. Plants from the field station showed no outcrossing, with progeny closely resembling the maternal parent, whereas plants from the wild population showed outcrossing with several different paternal parents. These results suggest self-pollinated seed can be reliably obtained in a plantation situation using stands of ramets of the same clone. Alternatively, assuming that the required insect pollinators are present in a cultivated stand, it should be possible to obtain cross pollinated seed by surrounding the maternal plant with the desired paternal parent. Unusual pollen behaviour was observed for many blue-flowered species, a white-flowered species of Conospermum, and close relative, Synaphea petiolaris. Up to three pollen tubes emerged from the triporate pollen in vitro, and at rates of up to 55 ƒÝms-1. This rate was maintained for only 2 s but is greater than 20 times faster than reported in the literature for any species, in vitro or in vivo. Pollen with multiple tubes was also observed on the stigma in vivo in C. amoenum flowers. Changing the osmotic pressure of the germination medium by altering sucrose concentration influenced the number of tubes to emerge from the pollen grain; generally the number of tubes decreased as sucrose increased. However, the rate of tube growth was unaffected. The addition of calcium channel blockers to the germination medium had no effect on Conospermum growth rate, nor did they eliminate pulses of tube growth. Observation of Conospermum pollen ultrastructure revealed similarities to Gramineae pollen. The tube cytoplasm was packed with vesicles filled with material of similar electron density to the cell wall. Few golgi were identified, and the apical end of the tube contained these vesicles, smaller secretory vesicles and mitochondria. This is atypical of the tip, which is normally free of large vesicles. Distinct zones in the cytoplasm were not identified, which is similar to Gramineae. Like the grasses, Conospermum appears to pre-manufacture cell wall material and store it in vesicles ready for rapid germination and extension. A biological function of multiple pollen tube emergence with such rapid growth was not elucidated. This research has shown Conospermum to be a complex and very interesting genus. Further investigation into the remarkable growth of multiple pollen tubes would enhance our knowledge of the biological processes involved in tube growth and the process of fast wall formation. The potential benefits to the cut flower industry of commercialising some of these species warrants further effort to find an efficient method of propagation. Introduction into horticulture may be the only means by which these threatened species will survive.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Anatomical Sciences, 2003. / "June 2003" Includes bibliographical references (leaves 408-457).

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 7 uppsatser.

Made available in DSpace on 2014-06-11T19:35:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-10Bitstream added on 2014-06-13T21:08:01Z : No. of bitstreams: 1 jesus_cm_dr_rcla.pdf: 5009514 bytes, checksum: ebcdbcc7d94f909d06c62d92fa2387e4 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Uma característica típica das formigas e algumas vespas é a presença das glândulas pós-faríngeas, estrutura que se encontra somente nesses grupos de organismos, fato que deve ter contribuído para o seu sucesso evolutivo. Apesar dos primeiros estudos com as glândulas pós-faríngeas existirem há mais de 100 anos, somente nos últimos 20 elas tem recebido maior atenção dos pesquisadores. Assim, a presente pesquisa teve por objetivo realizar uma análise comparativa da morfologia das glândulas pós-faríngeas e verificar sua participação na utilização de lipídeos ingeridos por três espécies de formigas com padrões alimentares distintos. Para tal, foi realizado análise ultramorfologica e ultraestrutural das glândulas pós-faríngeas; quantificação da ingestão de lipídeos e carboidratos, e verificação do trajeto destes compostos pelo sistema digestório das operárias; análise autorradiográfica do processo de incorporação do ácido oléico marcado radioativamente pelas glândulas pósfaríngeas das operárias. Os resultados encontrados sugerem que cada uma das espécies apresenta uma particularidade: as glândulas pós-faríngeas de Camponotus vittatus podem ser um sítio de reserva energética para o indivíduo; as operárias de Atta laevigata deslocam parte dos lipídeos ingeridos para o intestino médio, evitando o seu acúmulo nas glândulas pós-faríngeas, ao passo que foram encontradas pela primeira vez dois tipos de células nas glândulas pósfaríngeas de Pachycondyla villosa. Além disso, o trajeto percorrido pelos alimentos hidrossolúveis no interior do sistema digestório das operárias compreende a cavidade infrabucal, papo e ventrículo. Enquanto que os lipídeos passam pela cavidade infrabucal, glândulas pós-faríngeas e papo, mas não atingem o ventrículo; com exceção de A. laevigata em que foram encontrados... (Resumo completo, clicar acesso eletrônico abaix / A typical gland found only in ants and some wasps species is the postpharyngeal gland, which could have contributed to the evolutionary success of these social insects. The first studies regarding the morphology and function of the postpharyngeal glands were conducted about 100 years ago, and only in the last 20 years researches gave more attention to its importance. Thus, this study aimed at comparing the morphology of postpharyngeal glands and to verify their participation in the use of lipids ingested by three ant species. For this purpose, we performed: 1- Ultrastructural and Ultramorphology analysis of the postpharyngeal glands; 2 – the flow of lipids and carbohydrates inside the digestory systeam; 3 - the incorporation of radiolabeled oleic acid by the postpharyngeal using autoradiografic methods. Our results suggest that each species has a particularity: the postpharyngeal glands of Camponotus vittatus may be act as a site of food reserve, the workers of Atta laevigata prevent the accumulation of oleic acid in the postpharyngeal glands by sending lipids ingested to midgut. On the other hand, Pachycondyla villosa has specialized cells to eliminate of lipids from the postpharyngeal glands. Moreover, water-soluble diets were found in infrabucal pockets, crop and ventriculi, while lipid-soluble diets were found in infrabucal pockets, postpharingeal glands and crop; except for A. laevigata, which also had lipids in their midgut. Autorradiografic analysis showed that oleic acid is absorbed by the epithelium of... (Complete abstract click electronic access below)