PubMed · 14400637
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B HEILESEN. 1960. Diffuse goitre induced by PAS.. https://pubmed.ncbi.nlm.nih.gov/14400637/
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This study presents the morphology of the ovary, as well as the process of the vitellogenesis in oocytes of the tick Rhipicephalus sanguineus. The ovary of these individuals is of the panoistic type; therefore, it lacks nurse cells. This organ consists of a single tubular structure, continuous, and composed of a wall formed by small epithelial cells with rounded nuclei which delimit the lumen. The oocytes in the different developmental stages in this tick species were classified into five stages (I-V). They remain attached to the ovary during vitellogenesis by a cellular pedicel and afterwards the mature oocytes (stage V) are released into the ovary lumen.
A group of moderately halophilic bacteria able to degrade aromatic organic compounds contaminating hypersaline habitats in southern Spain have been isolated and characterized. The taxonomic position of these strains was determined using phenotypic, phylogenetic and genotypic methods. The G + C content of their DNA ranged from 61.0 to 62.9 mol%. DNA-DNA hybridization studies showed that they constitute a genospecies, having DNA-DNA hybridization values of 90-100 %. Analysis of the complete 16S rRNA gene sequence revealed a high level of similarity with members of the genus Halomonas, sharing 98 % 16S rRNA gene sequence similarity with the type strains of Halomonas salina and Halomonas halophila. However, phenotypic differences and the low level of DNA-DNA hybridization suggest the placement of these strains as a novel species within the genus Halomonas. The name Halomonas organivorans sp. nov. is proposed, with strain G-16.1T (= CECT 5995T = CCM 7142T) as the type strain. This novel species of Halomonas is characterized by its ability to use a wide range of organic compounds (benzoic acid, p-hydroxybenzoic acid, cinnamic acid, salicylic acid, phenylacetic acid, phenylpropionic acid, phenol, p-coumaric acid, ferulic acid and p-aminosalicylic acid), and it could be useful for the decontamination of polluted saline habitats.
The increasing rate of multidrug-resistant tuberculosis has led to more use of second-line antibiotics such as para-aminosalicylic acid (PAS). The mode of action of PAS remains unclear, and mechanisms of resistance to this drug are undefined. We have isolated PAS-resistant transposon mutants of Mycobacterium bovis BCG with insertions in the thymidylate synthase (thyA) gene, a critical determinant of intracellular folate levels. BCG thyA mutants have reduced thymidylate synthase activity and are resistant to known inhibitors of the folate pathway. We also find that mutations in thyA are associated with clinical PAS resistance. We have identified PAS-resistant Mycobacterium tuberculosis isolates from infected patients, which harbour mutations in thyA and show reduced activity of the encoded enzyme. Thus, PAS acts in the folate pathway, and thyA mutations probably represent a mechanism of developing resistance not only to PAS but also to other drugs that target folate metabolism.