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Estudo das interacoes dos produtos de radiolise da agua com a miotoxina do veneno de Crotalus durissus terrificus / Interaction study of water radiolisys products with crotalus durissus terrificus miotoxinSILVA, MURILO C. da 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:55:32Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:55Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Estudo das interacoes dos produtos de radiolise da agua com a miotoxina do veneno de Crotalus durissus terrificus / Interaction study of water radiolisys products with crotalus durissus terrificus miotoxinSILVA, MURILO C. da 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:55:32Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:55Z (GMT). No. of bitstreams: 0 / A radiação ionizante vem sendo empregada com sucesso na destoxicação de venenos. Neste trabalho a radiação foi utilizada para verificar os efeitos causados pelos produtos de radiólise da água na crotamina do veneno de Crotalus durissus terrificus. Estes efeitos foram analisados com o uso de algumas substâncias denominadas scavengers, que competem por espécies reativas específicas impedindo-as de agir na molécula. Para estudar, então, os possíveis danos estruturais causados às toxinas foram utilizadas as técnicas de dicroísmo circular, fluorescência, análise de ressonância nuclear magnética, análise de aminoácidos e análise de microscopia intravital. Os resultados obtidos demonstram que a radiação ionizante causa alterações estruturais importante nas estruturas secundárias e terciárias da crotamina. Também foi possível verificar que a toxina depois de irradiada não tem arranjo tridimensional detectável por ressonância nuclear magnética e ainda que o efeito tóxico da molécula é alterado quando a toxina foi irradiada. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Toxinas termo-lábeis (LTs) do tipo II de Escherichia coli enterotoxigênica (ETEC): efeito adjuvante e atividade inflamatória. / Type II heat-labile toxins (LTs) from enterotoxigenic Escherichia coli (ETEC): adjuvant effect and inflammatory activity.Camila Mathias dos Santos 23 September 2014 (has links)
Este trabalho realizou importantes avanços na elucidação do potencial das toxinas termo-lábeis do tipo II (LT-IIs) como adjuvantes por via intradérmica e transcutânea. Os dados gerados indicam que LT-IIb e LT-IIc nativas atuam como potentes adjuvantes vacinais por via intradérmica induzindo respostas imunológicas antígeno específicas, como medido pela produção de anticorpos sistêmicos (IgG) e ativação de linfócitos T CD8+ citotóxicos. Soma-se ao potencial adjuvante demonstrado para as LT-IIs por essa via a baixa reatogenicidade das moléculas, com menores níveis de edema e reduzida migração leucocitária para o sítio de inoculação em comparação a LT-I. Os resultados indicam também que o efeito adjuvante das LTs aplicadas por via transcutânea pode estar relacionado à capacidade de ligação ao gangliosídeo GM1 já que a toxina LT-IIb, incapaz de interagir com este receptor, não apresenta efeito adjuvante por essa via. O conjunto de dados apresentados abre perspectivas para o emprego das LT-IIs nativas como adjuvantes parenterais em vacinas para animais e humanos. / This work has made significant advances in the understanding of the potential of type II heat-labile toxins (LT-IIs) as vaccine adjuvants by intradermal and transcutaneous route. The generated data indicate that native forms of LT-IIb and LT-IIc act as potent vaccine adjuvants when intradermally injected inducing antigen-specific immune responses, as measured by the generation of systemic serum antibody (IgG) and activation of cytotoxic CD8+ T lymphocytes. Besides the adjuvant effects, LT-IIs show reduced side effects, measured by the lesser edema formation and reduced leukocytes migration to the site of injection, in comparison to LT-I. The results also indicate that the adjuvant activity of LTs applied transcutaneously may be related to the the ganglioside GM1 binding property since the LT-IIb toxin, unable to interact with this receptor, has no adjuvant effect by this route. The presented data set opens prospects for the employment of native LT-IIs as parenteral adjuvants in vaccines for animals and humans.
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Monitoração toxinológica do pescado comercializado nos municípios de São Sebastião e Caraguatatuba, SP / Toxinological monitoring of fisheries comercialized in São Sebastião and Caraguatatuba cities, São Paulo stateBruno Garcia Stranghetti 10 September 2007 (has links)
As toxinas do envenenamento paralisante por moluscos (Paralytic Shellfish Poisoning PSP) são compostos naturais bioativos conhecidos devido ao consumo acidental de frutos do mar contaminados. Estas moléculas, das quais a mais potente é a saxitoxina (STX), são uma classe de alcalóides neurotóxicos que possuem diferentes análogos e diferentes toxicidades, e são produzidas por algumas cianobactérias e algumas espécies de dinoflagelados do gênero Alexandrium, Gymnodinium e Pyrodinium. As toxinas paralisantes são neurotoxinas solúveis em água que agem sobre células nervosas e musculares através do bloqueio dos canais de sódio dependentes de voltagem, desta maneira, impedindo a condução do sinal no neurônio o que leva a uma paralisia muscular. Em casos graves, pode ocorrer morte por insuficiência respiratória. O envenenamento diarréico por moluscos (Diarrhetic Shelfish Poisoning DSP) é caracterizado por problemas gastrointestinais com sintomas como diarréia, náusea, vômito, dor de cabeça, calafrios e dores abdominais. DSP é conseqüência do consumo de mariscos contaminados que ingeriram dinoflagelados do gênero Dynophysis e Prorocentrun através de sua alimentação por filtração da água. Contaminação de frutos do mar por toxinas PSP ou DSP coloca-se como sério problema para a indústria pesqueira e para a saúde pública. Neste estudo, estabeleceu-se um programa de monitoração para mexilhões (Perna perna) e para peixes (Sardinella brasiliensis, Anchoviella lepidentostole e Brevoortia aurea) coletados em peixarias e entrepostos de pesca no municípios de Caraguatatuba e São Sebastião, São Paulo. Os extratos para PSP foram preparados de duas maneiras: de acordo com a AOAC (Association of Official Analytical Chemists), através do aquecimento por 5 min de uma mistura de 100 g de tecidos homogeneizados com ácido acético 0,1 N; ou a partir da concentração de extratos etanólicos de músculo + pele dos peixes. Os bioensaios com camundongos para PSP consistem na injeção intraperitonial de 1 mL do extrato ácido em cada um dos três camundongos (~ 20 g). O animal é observado quanto aos sintomas clássicos de PSP e o tempo de morte é anotado e então a toxicidade é determinada (em mouse units, MU) pela tabela de Sommer. Para as toxinas causadoras de DSP, os extratos foram preparados pela extração com acetona do homogeneizado das glândulas digestivas, e a determinação da presença destas toxinas é feita através da injeção intraperitonial em camundongos. Nos bioensaios com os extratos preparados segundo o método da AOAC, não houve casos positivos. Para o bioensaio realizado com extratos etanólicos obtiveram-se resultados positivos para 77,8% dos extratos testados. A média de MU de todas as amostras, neste caso, foi de 0,147 MU/g. Nos bioensaios para DSP, três amostras resultaram em sinais que evidenciam a presença destas toxinas, pois os camundongos injetados apresentaram quadro diarréico. Os extratos etanólicos, com positividade para as toxinas de PSP, foram fracionados usando-se colunas Sep-Pak C18. A primeira eluição, com ácido acético 0,1 M, foi analisada usando-se o método de préderivatização e cromatografia líquida de alta eficiência com detecção de fluorescência. As analises em CLAE indicaram a presença de compostos semelhantes às toxinas paralisantes de PSP, confirmando os bioensaios. Portanto, pela primeira vez no Brasil demonstrou-se que as espécies S. brasiliensis, A. lepidentostole e B. aurea são portadoras de toxinas paralisantes, semelhantes às PSP, em pequenas concentrações e que um programa de monitoração é necessário em nosso país para verificação da presença dessas toxinas em organismos que são usados como alimento pela população. / The Paralytic Shellfish Poisoning (PSP) toxins are well-known natural bioactive compounds due to their accidental consumption in contaminated seafood. These molecules, of which the most potent representative is saxitoxin (STX), are a class of neurotoxic alkaloids, having different isoforms and varied toxicities, that are produced by some cyanobacteria and some species of dinoflagellates from the genus Alexandrium, Gymnodinium and Pyrodinium. PSP toxins are water-soluble neurotoxins that act on nerve and muscle cells by blocking sodium channels voltage-dependent, thus preventing the conductance of neuron signal leading to muscular paralysis. In severe cases, death may result due to respiratory failure. Diarrhetic Shellfish Poisoning (DSP) is a gastrointestinal illness with symptoms such as diarrhea, nausea, vomiting, headache, chills and moderate to severe abdominal pain. DSP is usually a consequence of consuming contaminated shellfish that have ingested dinoflagellates of the genera Dinophysis and Prorocentrun through their filter feeding activities. Contamination of seafood by PSP and DSP toxins has posed serious problems to the fisheries industry as well to public health. In this study, was stabilized a monitoring program to shellfish (Perna perna) and finfish (Sardinella brasiliensis, Anchoviella lepidentostole and Brevoortia aurea) collected in fish markets in Caraguatatuba and São Sebastião cities, São Paulo state. The extracts for PSP were prepared by two ways: according to AOAC (Association of Official Analytical Chemists), through the heating for 5 min of blend of 100 g of well mixed sample with 0.1 N HCl; or through of the concentration of ethanolic extracts from finfishs muscle + skin. The PSP mouse bioassay for PSP toxins involves intraperitonial injection (i.p.) of 1 mL of the acid extract into each of three mice (~ 20 g). The mice were observed for classical PSP symptoms and the time to mouse death was recorded and the toxicity was determinate (in mouse units, MU) from the Sommers table. To DSP toxins, the extracts was prepared trough the extraction of digestive glands with acetone, and i.p injection in mice was used to determine the presence of theses toxins. In the mouse bioassay for the extracts prepared by AOAC method no positive results was obtained. For the mouse bioassay with ehtanolic extracts was obtained positive results to 77.8 % of the tested extracts. The media of MU of all samples, in this case, was 0,147 MU/g. To the mouse bioassay for the DSP toxins, three samples gives evidence of presence of the diarrhetic toxins, because the mice showed signal like diarrhea. The ethanolic extracts, that was positive to the PSP toxins, was fractionated by a Sep-Pak C18 cartridge. The first elution, with 0.1 M acetic acid, was analyzed by using prechromatographic oxidation and liquid chromatography with fluorescence detection. The HPLC analysis indicated the presence of the PSP toxins, confirming the bioassays. Therefore, in the first time in Brazil was demonstrated that the species S. brasiliensis, A. lepidentostole and B. aurea are carriers of toxins like PSP in little concentrations and that a monitoring program is necessary in our country to verify the presence of these toxins in organisms that are used as food by the population.
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Venomics of Sea Anemones: A Bioinformatic Approach to Tissue Specific Venom Composition and Toxin Gene Family Evolution.Macrander, Jason C. 26 September 2016 (has links)
No description available.
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Cardiovascular changes associated with intravenous administration of E. coli endotoxin in conscious poniesCox, Judy H. January 1984 (has links)
Call number: LD2668 .T4 1984 C68 / Master of Science
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The role of nitrogen in the regulation of microcystin content in Microcystis aeruginosaDowning, T. G. 12 1900 (has links)
Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Several genera of cyanobacteria produce a range of toxins. The increased
rate of eutrophication of surface fresh waters due to anthropogenic inputs has
resulted in more frequent and severe cyanobacterial bloom events. Such
bloom events make impoundments unsuitable for recreational use and
increase the cost of production of potable water due to the necessity for
removal of toxins released from cells during the purification process.
Microcystis aeruginosa is the major freshwater bloom-forming toxic
cyanobacterium. Concentrations of the hepatotoxin, microcystin, are highly
variable in blooms. Published literature on environmental conditions leading to
increased microcystin production was often contradictory and in many cases
did not consider all relevant parameters. However, environmental nitrogen
and phosphorus, temperature and light, and growth rate were implicated in
regulation of toxin content. The purpose of this work was therefore to
investigate environmental factors (specifically nitrogen and phosphorus) and
cellular activities (specifically carbon fixation and nitrogen uptake rates and
growth rate) involved in the modulation of microcystin production in M.
aeruginosa in order to clarify the role of these parameters, and in an attempt
to identify regulatory mechanisms for microcystin production. Environmental
nitrogen, phosphorus and growth rate were shown to co-modulate microcystin
production in M. aeruginosa. Adequate phosphorus is required for
photosynthetic carbon fixation. Phosphorus uptake by M. aeruginosa is
strongly correlated with carbon fixation rate. Although microcystin content
increased with increasing nitrogen:phosphorus ratios in culture medium,
under phosphorus limitation microcystin content was lower irrespective of
nitrogen concentrations. This observation and the requirements for fixed
carbon for nitrogen assimilation therefore prompted investigation of the effects
of cellular carbon fixation and nitrogen uptake in the modulation of microcystin
production. Microcystin production was found to be enhanced when nitrogen
uptake rate relative to carbon fixation rate was higher than that required for
balanced growth. The cellular nitrogen:carbon ratio above which microcystin
concentrations increased substantially, corresponded to the Redfield ratio for balanced growth. Investigation of potential regulatory mechanisms involving
the cyanobacterial nitrogen regulator, NtcA, yielded putative NtcA binding
sites indicative of repression in the microcystin synthetase gene cluster. In
culture, the polypeptide synthetase module gene, mcyA, and ntcA were
inversely expressed as a function of carbon-fixation:nitrogen-uptake potential.
However, no increase or decrease in microcystin production could be linked to
either glutamine, glutamate or a-ketoglutarate, metabolites that are involved in
regulation of ntcA. The role of NtcA in regulation of microcystin production
could therefore not be confirmed. In conclusion, these data suggest that
microcystin production is metabolically regulated by cellular C:N balance and
specific growth rate. The primary importance of nitrogen and carbon was
demonstrated by a simple model where only nitrogen uptake, carbon fixation
and growth rate were used to predict microcystin levels. The model also
explains results previously described in literature. Similarly, an artificial neural
network model was used to show that the carbon fixation dependence on
phosphorus allows accurate prediction of microcystin levels based on growth
rate and environmental nitrogen and phosphorus. / AFRIKAANSE OPSOMMING: Verskeie genera van sianobakterieë produseer 'n verskeidenheid van
toksiene. Die toename in die tempo van eutrofikasie van varswater
oppervlaktes as gevolg van antropogeniese insette veroorsaak al hoe meer
en al hoe erger sianobakteriële infestasies. Dit veroorsaak probleme vir
ontspanninggebruik van hierdie waters en verhoog die koste van produksie
van drinkbare water as gevolg van die noodsaak om die toksiene wat deur die
selle gedurende die suiweringsproses vrygelaat word te verwyder. Microcystis
aeruginosa is die belangrikste varswater bloeisel-vormende toksiese
sianobakterium. Die konsentrasie van die hepatotoksien mikrosistien is hoogs
varieerbaar in sulke bloeisels. Gepubliseerde literatuur oor die
omgewingskondisies wat lei na verhoogde mikrosistienproduksie is dikwels
weersprekend en neem in vele gevalle nie al die relevante parameters in ag
nie. Desnieteenstaande word omgewingstikstof, fosfor, temperatuur en lig,
asook groeisnelheid, geïmpliseer in die regulering van toksieninhoud. Die doel
van hierdie navorsing was dus om omgewingsfaktore (spesifiek stikstof en
fosfor) en sellulêre aktiwiteite (spesifiek koolstoffiskering en die snelheid van
stikstofopname en van groei) betrokke by die modulering van
mikrosistienproduksie in M. aeruginosa te ondersoek in 'n poging om die rol
van hierdie parameters te verstaan en om regulatoriese meganismes vir
mikrosistienproduksie te identifiseer. In hierdie studie is aangetoon dat
omgewingstikstof en fosfor sowel as groeisnelheid mikrosistienproduksie in M.
aeruginosa ko-moduleer. Genoegsame fosfor word benodig vir fotosintetiese
koolstoffiksering. Fosforopname deur M. aeruginosa korreleer sterk met die
snelheid van koolstoffiksering. Alhoewel mikrosistieninhoud toegeneem het
met 'n toename in die stikstof:fosfor verhouding in die kultuurmedium, was die
mikrosistieninhoud onder kondisies van fosforlimitering laer ongeag die
stikstofkonsentrasie. Hierdie waarneming, tesame met die noodsaak van
gefikseerde koolstof vir stikstofassimilering, het gelei na 'n studie van die
effekte van sellulêre koolstoffiksering and stikstofopname op die modulering
van mikrosistienproduksie. Dit is gevind dat mikrosistienproduksie verhoog
was wanneer die snelheid van stikstofopname relatief tot die snelheid van koolstoffiksering hoër was as die waarde wat benodig word vir gebalanseerde
groei. Die sellulêre stikstof:koolstof verhouding waarbo
mikrosistienkonsentrasies beduidend verhoog is stem ooreen met die
Redfield verhouding vir gebalanseerde groei. 'n Ondersoek na potensiële
reguleringsmeganismes waarby die sianobakteriële stikstofreguleerder NtcA
betrokke is het gelei na die ontdekking van moontlike NtcA bindingseteis; dit
kan dui op die repressie van die mikrosistiensintetase geengroepering. Onder
kultuurkondisies is gevind dat die geen vir die polipeptiedsintetase module,
mcyA, en ntcA omgekeerd uitgedruk word as 'n funksie van
koolstofopname:stikstofopname potensiale. Geen toename of afname in
mikrosistienproduksie kon egter gekoppel word aan óf glutamien, óf
glutamaat, óf a-ketoglutaraat nie, metaboliete wat betrokke is by die
regulering van ntcA. Die rol van NtcA in die regulering van
mikrosistienproduksie kon dus nie bevestig word nie. Die gevolgtrekking is
dus gemaak dat mikrosistienproduksie metabolies gereguleer word deur die
C:N balans en die spesifieke groeisnelheid. Die primêre belang van stikstof en
koolstof is gedemonstreer deur 'n eenvoudige model waarin slegs
stikstofopname, koolstoffiksering en groeisnelheid gebruik word om
mikrosistienvlakke te voorspel. Die model verklaar ook resultate wat tevore in
die literatuur beskryf is. Soortgelyk is 'n artifisiële neurale netwerkmodel
gebruik om te toon dat die afhanklikheid van koolstoffiksering van fosfor
akkurate voorspelling van mikrosistienvlakke gebaseer of groeisnelheid en
omgewingstikstof en fosfor moontlik maak.
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Capillary electrophoresis and related techniques for the analysis of fresh water algal toxins.John, Wilson. January 1997 (has links)
As cyanobacteria (also known as blue green algae) produce a range of cyclic peptides which
are highly toxic, capillary electrophoresis and associated techniques have been investigated
to assess their applicability for toxin monitoring in the water bodies of kwaZulu Natal,
South Africa. Capillary electrophoresis (CE) is a technique in which charged molecules can
be efficiently separated in a buffer solution within a capillary tube under the influence of a
strong electric field. Two CE modes, namely capillary zone electrophoresis (CZE) and
micellar electrokinetic capillary chromatography (MECC) were initially evaluated using a
laboratory-built CE instrument. The former mode lacked selectivity due to the similar
charge to size ratio of the algal toxins. However, with the latter mode, incorporation of a
surfactant (sodium dodecyl sulphate) into the buffer, produced sufficient resolution between
components. Parameters including surfactant concentration, buffer ionic strength, buffer
pH and operating voltage were systematically optimized to separate the four algal toxins
under investigation (microcystin YR, microcystin LR, microcystin RR and nodularin). The
optimum separation conditions were: 30 mM borax, 9 mM sodium dodecyl sulphate, pH
9.18, 30 kV applied voltage, 10 s hydrodynamic injection, 70 cm x 50 Ilm Ld. bare fused
silica capillary (LEFF 40 cm) and UV detection at 238 nm. Under these conditions, typical
detection limits were in the low ng/IlL range (14.13 ng/IlL for microcystin LR to 29.85
ng/ILL for nodularin).
The MECC method was evaluated in terms of migration time precision, efficiency and
resolution, peak area and normalised peak area precision. Standard deviation values for
retention times acquired using replicate electrokinetic injections ranged from 0.018 to 0.054
and 0.069 to 0.148 for hydrodynamic injections. Normalised peak area precision for
replicate hydrodynamic injections were in the range 84 to 97 % RSD, while improved %
RSD values of 11.5 to 18.7 were achieved for electrokinetic injections. Due to poor
precision resulting from the lack of automation on the laboratory built CE system, poor
correlation between increasing concentration and a corresponding change in normalised peak
areas were achieved. The MECC method developed was applied to the analysis of an algal
scum extract to illustrate the technique. A general problem with CE is that it suffers from poor detection sensitivity. Hence in this
study, alternative injection modes, sample concentration strategies and alternative detection
techniques were investigated in an attempt to improve detection limits for algal toxins.
Using optimized electrokinetic injection conditions, detection limits were five to ten times
better than those obtained with hydrodynamic injections. On-line sample concentration
methods were partially successful. Field amplified back and forth MECC in which analyte
injected in the entire column volume and subsequently focused in a narrow band by
manipulating the electric field, resulted in an enormous sensitivity enhancement that ranged
from 197 times for microcystin RR to 777 times for microcystin YR when compared to
hydrodynamic injections. Field amplified sample stacking (FASI) was ineffective for toxin
preconcentration, while electro-extraction produced detection limits ranging from 0.27
ng/J.tL for microcystin YR to 1.08 ng/J.tL for microcystin RR. Solid phase extraction, in
which analytes are first trapped and concentrated on HPLC material in a cartridge and then
eluted in a more concentrated form for injection, was found to be practical only in the offline
mode. A concentration detection limit of less than 0.002 ng/J.tL was obtained.
Attempts with on-line solid phase extraction failed due to problems associated with coupling
the cartridge with the separation capillary. Finally, laser induced fluorescence (LIF)
detection was investigated as an alternative to UV detection. Unfortunately, the algal toxins
were not amenable to LIF detection because tagging with the fluorescent moiety, fluorescein
isothiocyanate (FITC), was prevented by the stereochemistry of these cyclic peptides.
A comparative study between HPLC and MECC revealed that the former displayed poor
efficiency peaks and long analysis times for toxin analysis. However HPLC was superior in
terms of retention time precision (0.12 to 0.64 % RSD) and area precision (1.78 to 2.86 %
RSD). Mass detection limits for MECC (0.0142 to 0.0603 ng) were far superior to those
achieved by HPLC (0.55 to 1.025 ng). In addition to HPLC and MECC, a preliminary
investigation of micro-high performance liquid chromatography (J.tHPLC) and capillary
electrochromatography (CEC) for the analysis of algal toxins was made using 50 J.tm Ld.
capillary columns packed in-house, with reverse phase HPLC packing material. / Thesis (M.Sc.)-University of Natal, 1997.
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Ion selectivity and membrane potential effects of two scorpion pore-forming peptides / D. ElgarElgar, Dale January 2005 (has links)
Parabutoporin (PP) and opistoporin 1 (OP1) are cation, a-helical antimicrobial peptides isolated
from the southern African scorpion species, Parabuthus schlechteri and Opistophthalmus carinatus,
respectively. Along with their antimicrobial action against bacteria and fungi, these peptides show
pore-forming properties in the membranes of mammalian cells. Pore-formation and ion selectivity in
cardiac myocytes were investigated by measuring the whole cell leak current by means of the patch
clamp technique. Pore-formation was observed as the induction of leak currents. Ion selectivity of
the pores was indicated by the shift of the reversal potential (E,,,) upon substitution of intra (K' with
CS' and CI- with aspartate) and extracellular (Na' with NMDG') ions. Results were compared with
the effect of gramicidin A used as a positive control for monovalent cation selective pores. PP and
OP I induced a fluctuating leak current and indicate non-selectivity of PP and OP1-induced pores.
An osmotic protection assay to determine estimated pore size was performed on the cardiac
myocytes. PP and OP1-induced pores had an estimate pore size of 1.38-1.78 nm in diameter.
The effect of PP and OP1 on the membrane potential (MP) of a neuroblastoma cell line and cardiac
myocytes was investigated. TMRM was used to mark the MP fluorescently and a confocal
microscope used to record the data digitally. The resting membrane potential (RMP) of the
neuroblastoma cells was calculated at -38.3 f 1.9 mV. PP (0.5 uM) and OP1 (0.5-1 uM) depolarized
the entire cell uniformly to a MP of -1 1.9 k 3.9 mV and -9.4 k 1.9 mV, respectively. This occurred
after 20-30 min of peptide exposure. In the case of the cardiac myocytes depolarization was induced
to -39.7 f 8.4 mV and -32.6 f 5.2 mV by 0.5-1 uM PP and 1.5-2.5 uM OPl, respectively. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2006.
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Factors that impact Pseudo-nitzschia spp. occurrence, growth, and toxin productionDownes-Tettmar, Naomi January 2013 (has links)
This work investigates, for the first time, the Pseudo-nitzschia (PN) dynamics in the western English Channel (L4) and the environmental factors impacting on domoic acid (DA) production in these waters. This is combined with laboratory studies examining key environmental factors and the multifactorial impact of multiple macronutrient and micronutrient availability on PN growth and DA production. An LC-MS method was established, optimised, and compared with ELISA for the accurate and reproducible extraction and determination of particulate and dissolved DA. The method was used to measure the seasonal variation in DA at L4 during 2009 and this was compared to PN seasonal abundance and diversity. Three groups a P. delicatissima-group, a P. seriata-group, and a P. pungens/multiseries-group were identified and were found to have different ecological distributions with the latter two groups significantly correlating with DA concentration. Macronutrients, in combination with other environmental factors, were found to influence PN populations at L4. Multifactorial laboratory culture experiments investigating the availability of nitrate, phosphate, and silicate, confirmed that the interrelatedness of all these nutrients significantly affected the growth, decline, and DA production of P. multiseries, and highlight the importance of both phosphate and silicate availability for DA production. When the impacts of both macronutrient (phosphate and silicate) and micronutrient (iron and copper) availability were investigated, limited growth and DA production was observed in P. multiseries cultures. Results revealed the complexity and interrelationship of factors affecting both PN growth and DA production. Furthermore, molecular methods were developed to elucidate the PN species present from 2009 Lugol’s-preserved L4 samples. DNA was successfully extracted and amplified from these samples which had been stored for up to 2 years. Initial sequence analysis identified the rbcL DNA marker as an informative site for future work with a number of L4 sequences closely relating to different Pseudo-nitzschia spp.
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