The Diversity of Sulfide Oxidation and Sulfate Reduction Genes Expressed by the Bacterial Communities of the Cariaco Basin, Venezuela.

Qualitative expression of dissimilative sulfite reductase (dsrA), a key gene in sulfate reduction, and sulfide:quinone oxidoreductase (sqr), a key gene in sulfide oxidation was investigated. Neither of the two could be amplified from mRNA retrieved with Niskin bottles but were amplified from mRNA retrieved by the Deep SID. The sqr and sqr-like genes retrieved from the Cariaco Basin were related to the sqr genes from a Bradyrhizobium sp., Methylomicrobium alcaliphilum, Sulfurovum sp. NBC37-1, Sulfurimonas autotrophica, Thiorhodospira sibirica and Chlorobium tepidum. The dsrA gene sequences obtained from the redoxcline of the Cariaco Basin belonged to chemoorganotrophic and chemoautotrophic sulfate and sulfur reducers belonging to the class Deltaproteobacteria (phylum Proteobacteria) and the order Clostridiales (phylum Firmicutes).

The dynamics of the bacterial diversity in the redox transition and anoxic zones of the Cariaco Basin assessed by parallel tag sequencing.

Massively parallel tag sequencing was applied to describe the bacterial diversity in the redox transition and anoxic zones of the Cariaco Basin. In total, 14 samples from the Cariaco Basin were collected over a period of eight years from two stations. A total of 244 357 unique bacterial V6 amplicons were sequenced. The total number of operational taxonomic units (OTUs) found in this study was 4692, with a range of 511-1491 OTUs per sample. Approximately 95% of the OTUs found in the redox transition zone and anoxic layers of Cariaco are represented by less than 50 amplicons suggesting that only about 5% of the bacterial OTUs are responsible for the bulk of the microbial processes in the basin redox transition and anoxic zones. The same dominant OTUs were observed across all eight years of sampling although periodic fluctuations in their proportion were apparent. No distinctive differences were observed between the bacterial communities from the redox transition and anoxic layers of the Cariaco Basin water column. The largest proportion of amplicons belongs to Gammaproteobacteria represented mostly by sulfide oxidizers, followed by Marine Group A (originally described as SAR406; Gordon and Giovannoni 1996), a group of uncultured bacteria hypothesized to be involved in metal reduction, and sulfate-reducing Deltaproteobacteria. Gammaproteobacteria, Deltaproteobacteria and Marine Group A make up 67-90% of all V6 amplicons sequenced in this study. This strongly suggests that the basin's microbial communities are actively involved in the sulfur-related metabolism and coupling of the sulfur and carbon cycles. According to detrended canonical correspondence analysis, ecological factors such as chemoautotrophy, nitrate and oxidized and reduced sulfur compounds influence the structuring and distribution of the Cariaco microbial communities.

Intestinal uptake and toxicity evaluation of acetazolamide and its multicomponent complexes with hidroxypropyl-ß-cyclodextrin in rats.

Large oral doses of ACZ lower the intraocular pressure (IOP), but usually lead to a multitude of systemic side effects, including gastrointestinal upset. The present study was undertaken to evaluate the effect of ACZ on the histological structure of rat duodenal mucosa and to assess a possible protective role of the complex formation of ACZ with HP-ß-CD, either separately or in combination with a third compound, on the gut epithelial layer by histological and ultrastructural examinations of sections of rat duodenum exposed to ACZ or its formulations. In addition, the transport process of ACZ and its binary or ternary complexes across the duodenal mucosa by means of the single-pass intestinal perfusion (SPIP) method in rats was evaluated. Evidence was found that ACZ alters intestinal permeability and induces damage to the rat small intestine. In contrast, ACZ-induced intestinal injury may be abrogated by ACZ complexation. In addition, the complexation of ACZ with HP-ß-CD, alone or in combination with a third compound, facilitated significant levels of ACZ uptake across the rat duodenal segment. Ternary complexes of ACZ with HP-ß-CD in combination with TEA (triethanolamine) or calcium ions were found to provide an excellent approach that enabled an increased apparent permeability of ACZ across the duodenal epithelium, with a concomitant ability to preserve the integrity of the gut epithelium from ACZ-induced injury. These results could be useful for the design and development of novel ACZ formulations that can reduce GI toxicity, while still maintaining their essential therapeutic efficacies.

Characterization, dissolution and in vivo evaluation of solid acetazolamide complexes.

The effects of binary and ternary systems of acetazolamide (ACZ) with hydroxypropyl-ß-cyclodextrin (HP-ß-CD) alone or with triethanolamine (TEA) on the crystalline properties, dissolution and intraocular pressure (IOP)-lowering effect were investigated. It was found that the crystal structure of ACZ powder could be modified by the processing conditions. Freeze-drying ACZ powder affected not only the particle morphology but also its polymorphic form and the starting ACZ was converted to pure form A upon freeze-drying treatment. Results provided by DSC/TGA, XRPD, SEM and FT-IR suggested the formation of inclusion complexes between ACZ with HP-ß-CD alone or with TEA, obtained by the freeze-drying method and the conversion of the drug into the amorphous state. Binary and ternary systems of ACZ obtained by freeze-drying exhibited significantly enhanced ACZ dissolution rates. The IOP-lowering effects of ACZ and its complexes with HP-ß-CD alone or with TEA were studied in normotensive rabbits. Whereas the maximum IOP-lowering effect (~4 mmHg, ~33%), obtained with these binary and ternary lyophilized ACZ systems occurred at around 90 min, the ternary system exhibited a longer maximum IOP-lowering effect peak compared with that of the binary system. These results are in line with those obtained from the dissolution studies, where the ternary system exhibited longer dissolution times compared to the lyophilized binary one. Results obtained from the dissolution studies, also showed that freeze-drying the native crystalline form of ACZ significantly increased the dissolution rate of ACZ, thus improving the IOP-lowering effect of this drug.