Biomedical subjects

C E Ahnadi

Publications and source records attributed to C E Ahnadi.

7 recordsLinked to original sources

PubMed2001

Milk fatty acid composition and mammary lipid metabolism in Holstein cows fed protected or unprotected canola seeds.

Six midlactation Holstein cows were fed a total mixed ration supplemented with either 4.8% canola meal, 3.3% unprotected canola seeds plus 1.5% canola meal, or 4.8% formaldehyde-protected canola seeds, according to a double 3 x 3 Latin square design. Each period lasted 3 wk; experimental analyses were restricted to the last week of each period. Mammary biopsies were taken the last day of each period for gene expression measurements. Milk production and milk protein percentage were reduced by canola seeds, whether protected or unprotected. Protected canola seeds also decreased dry matter intake. Feeding canola seeds reduced the content of C8 to C16 fatty acids in milk and increased the content of oleic acid (C18:1c9). Unprotected canola seeds elevated the concentrations of C18:0. Protected canola seeds increased the C18:2 and C18:3 content, and reduced the C18d:0/C18:1c9 ratio. Similar results were obtained for plasma fatty acids, with some specific features, such as an increased C16:0/C16:1 ratio with protected canola seeds. Canola seeds had no significant effects on insulin, triglycerides, or cholesterol present in serum, but increased the concentration of nonesterified fatty acids; a greater increase was obtained with protected canola seeds. Expression levels of acetyl-CoA carboxylase and delta 9-stearoyl-CoA desaturase genes measured in the mammary gland did not differ significantly between diets. Therefore, the reduced C18s:0/C18:1c9 ratio observed in milk with protected canola seeds was not due to an enhanced expression of the delta-9 desaturase in the mammary gland.

Animal Feed↗

PubMed2000

Comparative multicentre study of a panel of thyroid tests using different automated immunoassay platforms and specimens at high risk of antibody interference.

The introduction of automation for immunoassays in recent years has brought about important and evident improvements in assay precision. Increasing standardization and comparability between platforms should enable the development of clinical guidelines and diagnostic algorithms for appropriate clinical decision making. A continuing source of variation between different automated immunoassay platforms is the sporadic effect of interfering antibodies or substances, thus causing aberrant results not supporting the patient's clinical status. The aim of this study was to describe current thyroid panel variation between automated immunoassay platforms including population specimens at risk of antibody interference. A multisite design with laboratories in three different countries using four different automated immunoassay platforms (Roche-Boehringer Mannheim Elecsys (Italy), Roche-Boehringer Mannheim ES300 (Wales), Bayer Immuno 1 and the Bayer ACS:180 evaluated the thyroid panel of thyrotropin (TSH), triiodothyromine (T3), free thyroxine (FT4) and free triiodothyronine (FT3). A common set of 158 randomly selected patient samples of non-thyroid and thyroid disorders, with and without treatment, was tested. Included were 62 patient samples at risk for endogenous antibody interference with high antimicrosomal antibody, anti-TSH receptor antibody and increased rheumatoid factor sub-populations. Across all controls and between platforms, precision measurements were comparable and varied between 0.7% and 12.8% for TSH, 2.8% and 13% for FT4, 1.8% and 10.5% for FT3 and 3.1% and 16% for T3 assay. Acceptable correlation and reproducibility were found between the three Bayer Immuno 1 platforms at each country's site with all four thyroid panel assays demonstrating r-values of 0.989 to 1.000 and slopes of 0.915 to 1.078. Comparisons between the different platforms showed acceptable correlation for all thyroid panel assays. Specimens containing rheumatoid factor were associated with a significantly increased variation between systems for the FT4 and FT3 assays (p < 0.01). This effect did not appear to be selective for a given platform. For specimens with raised autoimmune antibodies and therefore at risk of assay antibody interference, no variation could be observed between the platforms.

Antibodies↗

PubMed2000

Chronic PMA treatment of Jurkat T lymphocytes results in decreased protein tyrosine phosphorylation and inhibition of CD3- but not Ti-dependent antibody-triggered Ca2+ signaling.

We have treated Jurkat T lymphocytes with a concentration (160 nM) of phorbol myristyl acetate (PMA) that down-regulates conventional and novel protein kinase C (PKC) isozymes and we have investigated the effects on Ca2+ signaling and protein tyrosine phosphorylation using mAb (C305) directed against the beta-subunit of the Ti heterodimer or the epsilon/delta-component of the CD3 complex (mAb Leu 4 or OKT 3). The levels of expression of PKC alpha, betaI, betaII, and delta were reduced by 90% or more in PMA-treated cells, whereas the expression of PKCtheta decreased by approximately 30%. In contrast, the chronic treatment with PMA increased the expression of PKCepsilon and PKCzeta. There was a lack of Ca2+ response and myo-inositol trisphosphate (IP3) production in PMA-treated cells when they were exposed to mAb Leu 4 but the cells responded to mAb C305. The treatment with PMA did not affect the surface expression of Ti or CD3. The overall levels of tyrosine-phosphorylated proteins were markedly reduced in PMA-treated cells. We investigated whether these observations were related to defects in signal transduction related to protein tyrosine kinase (PTK) of the src and syk families. The electrophoretic mobilities of p59(fyn) or ZAP-70 were not changed in PMA-treated cells but p56(Ick) migrated as a large band of M(r) 60-62 kDa. The decreased mobility of p56(Ick) was related to a state of hyperphosphorylation. The activity of modified p56(Ick) was not up-regulated in activated Jurkat cells. Our data suggest that clonotypic Ti can trigger Ca2+ mobilization independently of conventional PKC isoforms. Our observations further suggest that conventional PKC isoforms are involved early in the cascade of events associated with Jurkat T lymphocyte activation.

CD3 Complex↗

PubMed1997

Signal transduction in Jurkat T lymphocytes. Evidence for early Ca2+ movements between the cytoplasm and the nucleoplasm in activated cells.

Spatial analyses of the distribution of Ca2+ in resting and activated T and B lymphocytes have shown that the bulk of increased [Ca2+]i appears to be associated with the nuclear region. These observations suggest that Ca2+ is released from the perinuclear space or that it diffuses to the nucleoplasm, or both. We have used laser scanning confocal microscopy to assess whether cytoplasmic diffusion of Ca2+ could contribute to the rise in nuclear Ca2+. We found that the activation of individual Jurkat cells by use of an anti-Ti (beta-subunit) mAb induced a nucleus-associated increase in [Ca2+]i. In cells loaded with the InsP3 receptor antagonist heparin, the nuclear Ca2+ response was abolished but not the response to thapsigargin. Evidence for a cytoplasmic Ca2+ response was obtained by loading Jurkat cells with a cytoplasm-restricted Ca2+ probe (Calcium Green-1-Dextran). These observations suggested that a process of diffusion of cytoplasmic Ca2+ contributed to the rise of nuclear Ca2+ in Jurkat T cells. This interpretation was supported by the findings (1) that rapid scanning of thapsigargin-released Ca2+ showed an inverse relationship between the levels of cytoplasmic and nuclear Ca2+ and (2) that modulation of the external concentration of Ca2+ in thapsigargin-treated Jurkat cells showed a time-dependent decrease of fluorescence from the nucleoplasm that was reversed by raising the concentration of external Ca2+. We conclude that Ca2+ can rapidly diffuse between the cytoplasm and the nucleoplasm in activated Jurkat T lymphocytes and that hydrophilic Ca2+ probes largely partition to the nucleoplasm, thus giving rise to distorted nucleus-to-cytoplasm fluorescence ratios.

Calcium↗

PubMed1996

Effects of staurosporine on the capacitative regulation of the state of the Ca2+ reserves in activated Jurkat T lymphocytes.

Staurosporine (Stp) is an inhibitor of protein kinase C (PKC) that has been used to address the role of this enzyme in a variety of cells. However, Stp can also inhibit protein tyrosine kinases (PTK). We have investigated the effects of Stp on the InsP3-(using mAb C305 directed against the beta chain of the T cell receptor (TcR/CD3 complex) and the thapsigargin (Tg)-dependent release and influx of Ca2+ in human (Jurkat) T cells. The addition of Stp (200 nM) during the sustained phase of the TcR-dependent Ca2+ response resulted in a rapid inhibition of the influx of Ca2+ that was not seen when Ca2+ mobilization was triggered by Tg (1 microM). When the cells were preincubated with Stp (200 nM), there was an inhibition of the mAb C305- but not the Tg-dependent Ca2+ response. The effect of Stp was not the result of the inhibition of PKC as shown by down-regulation of PKC and with the use of the specific PKC inhibitor bis-indolyl maleimide GF 109203X. The effect of Stp on the entry of Ca2+ in activated (mAb C305) Jurkat lymphocytes was dose-related and was not the result of a direct inhibition of plasma membrane Ca2+ channels based on an absence of effect on the Tg-dependent entry of Ca2+ and the use of Ca2+ channel blockers (econazole and Ni2+). These blockers terminated the influx of Ca2+ but the Tg-sensitive Ca2+ reserves were not refilled in marked contrast to the effect of Stp. Quantification of InsP3 revealed that the addition of Stp resulted in an approximate 40% reduction in mAb C305-activated Jurkat cells. The effects of Stp can be explained as follows. Stp decreases the mAb C305-induced production of InsP3 by inhibiting the TcR/CD3-dependent activation of PTK associated with the stimulation of phospholipase C-gamma 1. A decrease in [InsP3] without a return to baseline is sufficient to close the InsP3 Ca2+ channel, endoplasmic Ca2+ ATPases use the incoming Ca2+ to refill the Ca2+ pools and that terminates the capacitative entry of Ca2+. A simple kinetic model reproduced the experimental data.

Antibodies, Monoclonal↗

PubMed1993

Simvastatin-induced decrease in the transfer of cholesterol esters from high density lipoproteins to very low and low density lipoproteins in normolipidemic subjects.

Hyperlipidemic patients often have an accelerated esterified cholesterol transfer (ECT) from high density lipoproteins (HDL) to very low (VLDL) and low density lipoproteins (LDL). We investigated the effect of simvastatin on ECT in twelve normolipidemic subjects. After 6 weeks of simvastatin administration, ECT was decreased by 23%. To determine the mechanism of action of simvastatin, we measured ECT in different recombination experiments, using an isotopic assay in which the transfer of labelled EC from HDL to VLDL/LDL was determined. When HDL of the treated subjects were incubated with VLDL/LDL and CETP fractions isolated from control plasma, no effect of simvastatin was observed, indicating that the drug did not alter the HDL-dependent ECT. This might be expected since simvastatin induced only minor modifications of HDL structure. When HDL and VLDL/LDL of control plasma were incubated with CETP fractions of the treated subjects, a clear reduction of ECT occurred after simvastatin administration. The decrease of plasma transfer activity was correlated to that of CETP concentration and accounted for the simvastatin-induced lowering of ECT. The diminution of plasma CETP was correlated to that of the apo B-containing lipoproteins concentration. This finding confirms previous reports suggesting a relationship between LDL level and CETP activity. In conclusion, our work shows that simvastatin administration results in a decrease of ECT and that this effect occurs through a lowering of plasma CETP activity.

Adult↗

PubMed1993

Decreased ability of high density lipoproteins to transfer cholesterol esters in non-insulin-dependent diabetes mellitus.

Esterified cholesterol transfer (ECT) from high density lipoproteins (HDL) to very low (VLDL) and low density lipoproteins (LDL) may be abnormal in situations at high risk for atherosclerosis. It has been shown to increase in insulin-dependent diabetes and to decrease in non-insulin-dependent diabetes (NIDD). Since the net transfer of esterified cholesterol (EC) results from a bidirectional exchange between HDL and VLDL/LDL, we developed a transfer assay specifically designed to measure the unidirectional transfer of EC from HDL to lipid emulsions according to first-order kinetics. Our results show that in NIDD the rate constant of HDL-dependent ECT is decreased by 30% by comparison with control subjects. Analysis of HDL composition revealed that, in both groups, HDL-dependent ECT was positively correlated with the free cholesterol/phospholipid ratio (r = 0.94; P < 0.001) and negatively correlated with the triglyceride/EC ratio (r = -0.85; P < 0.001). It is concluded that, besides the known defect of acceptor lipoproteins, the abnormality of ECT in NIDD is also caused by a decreased ability of HDL to act as an EC donor, presumably because of a change in composition. In addition, our work shows that the amount of EC lost by HDL during the reaction transfer is counterbalanced by a reciprocal equimolar transfer of triglycerides.

Cholesterol Esters↗