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Abstract

Objective—To assess the effects of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) on functions of mononuclear cells obtained from ewes.

Animals—6 Sardinian ewes.

Procedure—Mononuclear cells were cultured with concentrations of NEFA (0, 15.6, 31.2, 62.5, 125, 250, 500, 1,000, or 2,000 µmol/L) and BHBA (0, 0.45, 0.9, 1.8, or 3.6 mmol/L). Concentrations of NEFA and BHBA were intended to mimic those of ketotic or healthy ewes, and NEFA and BHBA were tested alone and in combination. Synthesis of DNA was stimulated by use of concanavalin A (Con A) or pokeweed-mitogen (PWM). Secretion of IgM was stimulated by use of PWM.

Results—Synthesis of DNA stimulated by Con A and PWM was significantly inhibited by high concentrations of NEFA (≥ 250 µmol/L) or by a combination of high concentrations of NEFA (≥ 250 µmol/L) and all concentrations of BHBA (≥ 0.45 mmol/L). In contrast, DNA synthesis was not inhibited by low concentrations of NEFA (≤ 125 µmol/L) or by a combination of low concentrations of NEFA (≤ 125 µmol/L) and the lowest concentration of BHBA (0.45 mmol/L). Secretion of IgM was significantly inhibited by all concentrations of NEFA and by all combinations of NEFA and BHBA concentrations. When used alone, none of the concentrations of BHBA inhibited DNA synthesis or IgM secretion.

Conclusions and Clinical Relevance—Reduced immunoresponsiveness during ketosis is likely to be associated with an increase in plasma concentration of NEFA and not with an increase in plasma concentration of BHBA. (Am J Vet Res 2002;63:414–418)

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in American Journal of Veterinary Research

Abstract

Objective—To assess effects on functions of peripheral blood mononuclear cells (PBMC) obtained from ewes for each of several fatty acids represented in ovine plasma at concentrations mimicking those of ketotic or healthy ewes.

Sample Population—Blood samples obtained from 6 Sardinian ewes.

Procedure—The PBMC were cultured in media that contained oleic (OA), palmitic (PA), stearic (SA), linoleic (LA), or palmitoleic (POA) acid at concentrations similar to those of ketotic or healthy ewes. Synthesis of DNA was stimulated by use of concanavalin A or pokeweed mitogen (PWM). Secretion of IgM was stimulated by use of PWM.

Results—High concentrations (900, 450, and 225 µmol/L) of OA significantly inhibited DNA synthesis and IgM secretion of PBMC. Conversely, low concentrations (56 or 28 µmol/L) of OA significantly enhanced DNA synthesis of PBMC. High concentrations of PA (600, 300, 150, 75, 37.5, or 18.7 µmol/L) and SA (300, 150, or 75 µmol/L) significantly inhibited DNA synthesis of PBMC. High concentrations of PA (600, 300, 150, 75, 37.5, or 18.7 µmol/L) and SA (300, 150, 75, or 38 µmol/L) also significantly inhibited IgM secretion of PBMC. None of the concentrations of LA and POA affected PBMC functions.

Conclusion and Clinical Relevance—Impaired immunoresponsiveness of ketotic ewes is likely associated with an increase of plasma concentrations of OA, PA, or SA and not with that of LA or POA. At physiologic concentrations, single fatty acids are likely to participate in modulation of immunoresponsiveness by exerting suppressive or stimulatory effects on immune cells. (Am J Vet Res 2002;63:958–962)

Full access
in American Journal of Veterinary Research