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S Neto

Publications and source records attributed to S Neto.

4 recordsLinked to original sources
PubMed2000

Asymmetric synthesis of 2-methyl cyclohexane carboxylic acids by heterogeneous catalysis: mechanistic aspects

The catalytic hydrogenation of (S)-alkyl-N-(2-methylbenzoyl)pyroglutamates was studied over supported rhodium and ruthenium catalysts at room temperature and a pressure of 5 MPa. The reaction was diastereoselective with the predominant formation of (1S,2R)-2-methylcyclohexane carboxylic acid with a diastereomeric excess (de) of up to 96%. The most stable conformation was determined by means of a combination of modelling calculations, NMR spectroscopy and X-ray structural determination. In this conformation, the carbonyl group of the pyroglutamate auxiliary shields one face of the aromatic ring. The observed selectivity may thus be explained by a preferential adsorption at the unshielded face which avoids steric repulsion by the C=O group to result in a cis hydrogenation. The addition of an amine, the nature of the support (alumina or active carbon) or of the metal (Rh or Ru) were shown to give additional stabilisation of the adsorption at the unshielded face to increase the diastereoisomeric excess.

Journal Article↗
PubMed1998

Cytokine analysis of human renal allograft aspiration biopsy cultures supernatants predicts acute rejection.

BACKGROUND: A Th1 response is said to be associated with transplant rejection and Th2 with tolerance, although this is not agreed by all. Cytokines evaluation in peripheral blood and urine in kidney transplants produces variable results. We hypothesized that measurement of major cytokines involved in Th1/Th2 paradigm on transplant renal-infiltrating cells could bring valuable scientific and clinical information. METHODS: Fifty-six adult cadaver kidney transplants were subdivided into 21 stable patients (group A), 22 suffering acute rejection (group B), 10 with chronic rejection (group C) and three with CMV disease (group D). Fine-needle aspiration biopsies were cultured and their supernatants analysed for IL-2, IL-4, IL-10 and IFN-gamma. RESULTS: Group A produced small amounts of both IL-2 and IL-10 while group B synthetized significantly higher IL-2 and significantly lower IL-10 amounts than group A. Group B produced significantly more IL-2 than A on day 7 post-transplantation, several days before rejection supervened. Group C produced IL-10 and very low amount of IL-2. Group D produced both IL-2 and IL-10. We did not find any IL-4, and IFN-gamma was present in a few samples. For IL-2, sensitivity, specificity, negative and positive predictive values for acute rejection were 100, 87.2, 94.7 and 83.3%, respectively. CONCLUSIONS: Cytokine analysis in fine-needle aspiration biopsy cultures supernatants is a very useful immunological screening method for kidney transplants. IL-2 synthesis on day 7 post-transplantation reliably predicted the risk of impending acute rejection during the first weeks. The cytokine pattern suggests that acute rejection is associated with Th1, stable patients with Th0/Th2, and chronic rejection with Th2 patterns.

Acute Disease↗
PubMed1997

Monocytes-macrophages and cytokines/chemokines in fine-needle aspiration biopsy cultures: enhanced interleukin-1 receptor antagonist synthesis in rejection-free kidney transplant patients.

BACKGROUND: Monocytes-macrophages are found within kidney allografts during the first days after surgery, where they perform "housekeeping" tasks, participate in postreperfusion injury, and act as antigen-presenting cells, as well as become involved in the effector phase of acute rejection. They also seem to play a prominent role in chronic rejection. We quantified their presence in fine-needle aspiration biopsies and studied the growth factors that, we hypothesized, would mark the different implications of the presence of monocytes-macrophages. METHODS: Fine-needle aspiration biopsies were obtained from 56 adult renal transplants and analyzed for CD14+ using the alkaline phosphatase-anti-alkaline phosphatase procedure. Thirty-three patients were studied on the production of interleukin (IL)-1 receptor antagonist (IL-1ra), IL-6, IL-8, macrophage colony-stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1alpha by aspiration biopsies cultures using enzyme-linked immunosorbent assay techniques. RESULTS: CD14+ cells were present at significantly higher numbers in steroid-resistant acute rejections but also during the first days after surgery, especially if acute tubular necrosis was present. We found a significantly higher production of IL-1ra by rejection-free patients compared with acutely rejecting patients, and this difference was already established on day 7 after surgery (10+/-10.5 days before rejection). CONCLUSIONS: Monocytes-macrophages are present at higher numbers in aspiration biopsies of kidney transplant patients suffering either acute tubular necrosis or steroid-resistant rejections, but they are present during the first days after transplant in stable patients, too. The production of IL-1ra is significantly up-regulated in stable patients, which suggests that monocytes-macrophages may constitute an early key factor in the down-regulation of the anti-allograft immune response.

Adolescent↗