This thesis is missing page 57, no other copy of the thesis contains this page. -Digitization Centre / The experiments in this thesis were undertaken to: 1) compare the effects of cycloheximide and azaserine on asparagine synthesis in root-tip sections of corn; 2) study the effect of protein synthesis on asparagine synthesis in root-tip sections by the use of analogues of cycloheximide; and 3) study the properties of asparagine synthetase extracted from corn roots.When [2-1 4c]-acetate is fed to excised root-tip sections of corn pre-incubated in the presence of cycloheximide, protein synthesis is inhibited. The effect is almost immediate. Within the amide fraction, the levels of glutamine formed in these sections rises over the 3 hour pre-incubation period. Asparagine synthesis gradually declines over the same period. In similar experiments performed with azaserine in the pre-incubation media, protein synthesis was not markedly inhibited. Glutamine levels were immediately increased over the 3 hour period. The effect on asparagine synthesis was also rapid. In contrast to the situation with cycloheximide, the effect of azaserine on amide synthesis is constant over a 3 hour period. Two analogues of cycloheximide - cycloheximide acetate and streptovitacin A - were found to produce effects similar to that of cycloheximide. These analogues were found to inhibit both protein synthesis and asparagine synthesis after a 3 hour exposure period. Six other analogues did not show marked inhibitory effects on either protein synthesis or asparagine synthesis. Asparaqine synthetase activity was found in extracts from corn seedling tissues.. However, assays for asparagine synthetase revealed that the activity was low and 'that other aspartate utilizing enzymes were probably active in the extracts. From the results of this investigation and those of earlier published results a model has been proposed in order to explain the regulation of asparagine synthesis in corn roots. / Thesis / Master of Science (MS)

No description available.

The acquisition of a behavioural response (learning) and the later retrieval of this response (memory) are separated by an endogenous biological process which consolidates the temporary neural changes initiated by training. Intracerebral infusions of stimulants to the hippocampus potentiate this process and infusions of protein synthesis inhibitors (PSIs) impair it. A tacit assumption regarding the application of PSIs is that they have no effect upon spontaneous brain electrical activity; however, given their documented non-specific side effects, this idea was re-evaluated under controlled conditions. Hippocampal recordings were made in urethane anaesthetized rats before and after unilateral hippocampal infusions of the PSIs anisomycin and cycloheximide. Infusions suppressed local field potentials, eliminated sink/source alternations and silenced multiunit activity without affecting the contralateral hippocampus. This suppression was correlated with the degree of protein synthesis inhibition. These results present a serious confound for all results obtained using anisomycin and cycloheximide to test memory consolidation.

No description available.

Made available in DSpace on 2014-10-09T12:55:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:00Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:06/52973-9

Made available in DSpace on 2014-10-09T12:55:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:00Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A Prolactina humana hPRL é um hormônio protéico com 199 aminoácidos (MM ~ 23.000 Da) com um amplo espectro de atividades biológicas, sendo mais conhecido por estimular a lactação e regular o crescimento e diferenciação da glândula mamária. Além de quebra proteolítica, a maioria dos variantes de prolactina podem ser resultantes de outros processos pós-traducionais como polimerização, fosforilação, desamidação, sulfatação e glicosilação. Essa proteína contém apenas um sítio potencial de glicosilação por ligação à asparagina, localizada no aminoácido 31, que é parcialmente ocupado (10%) quando a proteína é sintetizada em células eucariotas. Apesar da atividade biológica in vitro da prolactina glicosilada (G-hPRL) ser muito menor (~4 vezes) quando comparada à não glicosilada, sua função fisiológica ainda não é bem definida e a porção de carboidrato parece ter um importante papel na biossíntese, secreção, atividade biológica, e clearance plasmático do hormônio. Com o objetivo de melhor caracterizar e estudar esta variante hormonal, foi realizada sua purificação em escala laboratorial a partir de células de ovário de hamster chinês (CHO) modificadas geneticamente, utilizando meio de cultura suplementado com cicloheximida, aumentando ~4 vezes sua concentração absoluta e ~10 vezes a razão entre a isoforma glicosilada e a não-glicosilada. A purificação da G-hPRL seguiu um processo simples e efetivo de duas etapas principais baseado em uma coluna de troca catiônica e uma coluna preparativa de exclusão molecular acoplada a um sistema de cromatografia líquida de excusão molecular de alta eficiência (HPSEC). A caracterização foi feita por HPLC de fase reversa (RP-HPLC) e exclusão molecular, SDS-PAGE, Western Blotting, espectometria de massa (MALDI-TOF) e um bioensaio in vitro utilizando células Nb2 e Ba/F3-LLP. Nossos resultados demostram que a cicloheximida pode ser uma importante ferramenta para aumentar a produção de prolactina glicosilada, facilitando a purificação e caracterização dessa isoforma. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:06/52973-9

No description available.

The formation of synapses in cell cultures of rat cerebellum was examined in the presence of the protein synthesis inhibitor cycloheximide. First, cell survival in the presence of 25 μg/ml cycloheximide was determined by phase contrast microscopy, trypan blue exclusion, total protein and uptake of [3H]gamma-aminobutyric acid (GABA). Neurons with 24 h incubation in cycloheximide appeared normal with little cell death, but by 48 h incubation the first signs of cell death were found. Some viable neurons were still found in cultures incubated continuously in cycloheximide for 72 h. Normally, the number of synapses seen in cerebellar cultures with the electron microscope shows an increase during the first several weeks in culture. However, the number of synapses in cultures treated with cycloheximide decreased, indicating that inhibition of protein synthesis at least partially inhibited synaptogenesis. Cycloheximide also inhibited the maintenance of synapses already formed as seen by the decrease in the number of synapses from the time the cycloheximide was added. To determine the sensitivity of the forming presynaptic element to cycloheximide, the development of apparent presynaptic elements was investigated. In cultures treated with polylysine-coated sepharose beads, neurites grew and formed apparent presynaptic elements with the bead taking the position of the postsynaptic element. Cultures pretreated with cycloheximide for 1 h followed by 24 h incubation with both cycloheximide and coated beads showed a normal number of apparent presynaptic elements. The first decrease in numbers was seen after 12 h preincubation and 12 h incubation with both cycloheximide and coated beads. Even after 72 h continuous incubation some apparent presynaptic elements could be formed although at reduced levels. Results presented here suggest that continuous protein synthesis is not necessary for the formation of the presynaptic element, but that active protein synthesis is required for neurons to form and maintain postsynaptic elements.

Upon exposure to heat or cold, Arabidopsis thaliana seedlings undergo rapid transcriptional reprogramming of several hundreds of genes that promote stress tolerance. Despite extensive characterisation of the transcriptional responses to these stimuli, however, relatively little is known about the mechanisms by which temperature signals are perceived and transduced in plant cells. High or low seasonal temperatures have large impacts on crop productivity and are expected to intensify given current global climatic projections. It is therefore of agricultural importance to better understand temperature signalling pathways in plants in order to find solutions to this problem. In this thesis, a chemical genomics screen for molecules activating or repressing heat-inducible genes in A. thaliana was performed in collaboration with Syngenta and the biological targets of these chemicals were predicted based on structural similarities to compounds with known modes of action. Many molecules that affect the function of chloroplasts or mitochondria either activate or repress heat-responsive genes, thus implicating these organelles in the regulation of plant temperature responses. In addition, the translation inhibitor cycloheximide was identified as a repressor of heat-inducible genes and an activator of early cold-inducible genes. Diverse translation inhibitors trigger a cytosolic influx of calcium ions and several inhibitors of translation elongation were found to strongly activate cold-inducible gene expression in a calcium-dependent manner. Furthermore, it was demonstrated that cold shock causes rapid translation repression in A. thaliana seedlings and that the elongation factor LOS1 is involved in cold- or cycloheximide-induced gene expression, thus implicating translational machinery in the regulation of temperature signalling in plants. Finally, one of the chemicals identified in the screen, S01A463859Y, was found to improve heat resilience in A. thaliana and may therefore be of potential use in enhancing crop productivity during thermal stress.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.