The intertidal mussels. Perna perna and Choromytilus meridionalis co-occur on the southern coast of South Africa. Mussels ingest mixtures of bacteria. phytoplankton. zooplankton and detritus. with proportions varying according to availability. These bivalves filter similar-sized particles. which might result in interspecific competition. Carbohydrate-digesting enzymes of the mussels and their enteric bacteria. and bacteriolytic enzymes of the mussels were therefore examined to elucidate feeding ecology in these animals at an enzymatic level. Style enzymes of both species digested the storage carbohydrates amylose glycogen and laminarin, and the structural carbohydrate carboxymethyl cellulose (CMC). Differential rates of digestion of these carbohydrates suggests that Perna perna relies more on plankton (and possibly bacteria) than on detritus for food while Choromytilus meridionalis relies equally on all components of the seston. There may therefore be some degree of resource partitioning of the seston. The styles of P.perna had a lower specific enzyme activity. but higher protein content than those of C.meridionalis. P.perna could therefore release more glucose from a given concentration of substrate than C.meridionalis. The gut contents and tissue were examined microscopically to determine where the bacterial colonisation sites were. Bacteria were associated primarily with the gut contents but not the gut walls. of both species. The styles housed spirochaete bacteria (Crislispira sp), Perna perna housed large numbers of one species. while Choromytilus meridionalis had lower numbers of two species. Levels of infection differed between species and localities. Enteric (but not style) bacteria of Perna perna and Choromytilus meridionalis always digested the same carbohydrates as the mussels as well as the structural carbohydrates mannan and fucoidan. Activity was erratic on the structural compounds, carageenin and xylan, and absent on alginic acid or inulin. Activity on the storage carbohydrates by enteric bacteria from C.meridionalis was higher than by those from P.perna. This is probably related to the larger bacterial populations housed by C.meridionalis than by P.perna. Bacteriolytic activity by the digestive enzymes of Pema perna was higher than for Choromytilus. In P.perna it was due to a combination of different enzymes one of which is a true lysozyme. C.meridionalis did not produce a true lysozyme. Enzymes produced by the mussels and their enteric bacteria allow the mussels to utilise all components of the seston. Low endogenous enzyme activity by Choromytilus meridionalis, coupled with the high activity by its enteric bacteria, suggests that they rely more on bacterial activity to meet their dietary requirements than does Perna perna. The ability of enteric bacteria to digest carbohydrates which the mussels cannot indicates that the bacteria are endosymbiotic, although the sporadic nature of activity of some of the enzymes, and the fact that bacteria are associated with the gut contents, indicates that the relationship is only incidental.

Thesis (M.Sc.(Biochemistry))--University of Pretoria, 2003. / Includes summary. Also available online.

Orientadores: Rogério de Castilho Jacinto, Brenda Paula Figueiredo de Almeida Gomes / Texto em português e inglês / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-22T14:36:20Z (GMT). No. of bitstreams: 1 Rosa_TiagoPereirada_M.pdf: 1839317 bytes, checksum: 3802ff7b07872cf4f364ef3f4fd5d1d7 (MD5) Previous issue date: 2013 / Resumo: Infecções extrarradiculares representam um obstáculo para o reparo dos tecidos apicais após o retratamento endodôntico não-cirúrgico. Treponemas são espiroquetas anaeróbias estritas, fastidiosas, de difícil cultivo em condições laboratoriais, que já foram encontradas em canais radiculares infectados e em abscessos apicais agudos. Este estudo investigou a presença de T. socranskii, T. maltophilum, T. amylovorum, T. medium, T. lecithinolyticum, T. denticola, T. vicentii e T. pectinovorum em lesões periapicais associadas ao insucesso do retratamento endodôntico; sua associação com as características clínicas/radiográficas; e a associação entre essas espécies. Amostras microbiológicas foram coletas das lesões periapicais de 25 pacientes adultos encaminhados para cirurgia apical após o insucesso do retratamento endodôntico. Nested-PCR e PCR convencional foram utilizados para a detecção das espécies. Vinte e três amostras apresentaram níveis de DNA bacteriano detectáveis. Treponemas foram identificados em 28% (7/25) dos casos. A espécie mais frequentemente encontrada foi T. socranskii (6/25), seguida por T. maltophilum (3/25), T. amylovorum (3/25), T. Lecithinolyticum (3/25), T. denticola (3/25), T. pectinovorum (2/25) e T. medium (2/25). T. vicentii não foi detectado em nenhuma amostra. Foi encontrada uma associação estatística positiva entre T. socranskii e T. denticola, T. maltophilum e T. Lecithinolyticum. Nenhuma associação significativa foi observada entre os microrganismos pesquisados e as características clínicas e radiográficas. Conclui-se que Treponemas são encontrados em lesões perirradiculares de dentes com insucesso do retratamento endodôntico e podem participar da comunidade microbiana associada à manutenção do processo inflamatório nos tecidos periapicais / Abstract: Extraradicular root canal infections represent an obstacle to the resolution of the infectious process after nonsurgical endodontic retreatment. Treponema species, which are fastidious strict anaerobic spirochetes difficult to grow under current laboratory conditions, have been found in root canal infections and acute apical abscesses. This study investigated the presence of Treponema species in endodontic retreatment-resistant apical periodontitis; their association with the clinical/radiographic features; and the association between the target species. Microbial samples of periradicular lesions were collected from twenty-five adult patients referred to endodontic surgery after unsuccessful root canal retreatment. Nested-PCR and conventional PCR were used for Treponema detection. Twenty-three periradicular tissue samples showed detectable levels of bacterial DNA. Treponema species were detected in 28% (7/25) of cases. The most frequently species were T. socranskii (6/25) followed by T. maltophilum (3/25), T. amylovorum (3/25), T. lecithinolyticum (3/25), T. denticola (3/25), T. pectinovorum (2/25) and T. medium (2/25). T. vicentii was not detected in any sample. Positive statistical association was found between T. socranskii and T. denticola, T. maltophilum and T. lecithinolyticum. No association was detected between any target microorganism and the presence of clinical or radiographic features. In conclusion, Treponema spp. are present in periapical lesions from teeth with failure of the endodontic retreatment and can participate in the microbial communities associated with the maintenance of the inflammatory process in the apical tissues / Mestrado / Endodontia / Mestre em Clínica Odontológica

The fungus Diplodia maydis, (synonym Stenocarpella maydis (Berk)) is worldwide one of the most important cob rot pathogens of maize. The isolation of stenocarpin, a metabolite toxic to ducklings, from maize cultures of D. maydis as the 4,6-0-diacetate derivative and its structure elucidation has been reported in the literature. Detailed NMR studies established the structure as either (3S,4R,6R,7R)- or (3R,4R,6R,7R)-spiro[(4,6, 7-trihydroxy-7-methyl-8-oxo-5,6,7,8-tetrahydroisochromane)-3 ,2' -tetrahydrofuran]. The absolute configuration of the C(3) spiroacetal stereogenic center remained unknown. The aim of the synthetic studies described in this dissertation was to develop a synthetic methodology for the spiroacetal moiety present in stenocarpin in order to establish unambiguously the C(3) absolute configuration. Retrosynthetic analysis of stenocarpin identified two model compounds (5S,lOR)- and (5R,lOR)-1,6-dioxaspiro[4.5]dec-8-en-10-o1 as the synthetic target. In turn the retrosynthetic analysis of these model compounds led to commercially available L-arabinose as starting material. Two strategies, which differ in the timing for the formation of the spiroacetal moiety as well as the initial type of protecting groups, were employed in the development of the synthetic route. In the first route the spirocyclisation reaction of a benzyl protected intermediate followed by the syn elimination of the cis-diol group resulted in the formation of only the (5S, lOR) model compound. The use of the acetonide and TBDPS protecting groups from the outset of the synthetic route and once again a spirocyclisation reaction, led to the formation of two spiro compounds epimeric at the C(5) spiro stereogenic centre, which could be separated and transformed by a syn elimination of the cis-diol group to the two model compounds. The configuration of the spiroacetal intermediates formed in the two synthetic routes and the changes in conformation that occurred in each of the steps were deduced from extensive NMR studies and especially the NOE technique. The results established the 3S configuration for stenocarpin and provided a viable synthesis for the (5S,lOR)-l,6-dioxaspiro[4.5]dec-8-en-1O-ol model compound that is to be used in the total synthesis of stenocarpin. In the dissertation the results of the first steps in a total synthesis, a study on the epoxidation of the double bond, is presented. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted