Immunomodulatory effect of xylazine, an alpha(2) adrenergic agonist, on rat spleen cells in culture.

Xylazine is an adrenergic alpha(2) agonist, which is used in veterinary medicine as a sedative and anesthetic agent. In this work we found that xylazine administered in vivo at a dose of 2.5 mg/kg enhanced spleen cell proliferation and interleukin 2 (IL-2) production in cultures stimulated with concanavalin A (Con A), whereas doses of 10 and 25 mg/kg were inhibitory. A similar stimulatory (10 microM) and inhibitory (50-500 microM) effect on splenocyte proliferation and IL-2 production was observed in vitro. Clonidine, another alpha(2) adrenergic agonist, only had a stimulatory proliferative effect on splenocytes. Yohimbine, an alpha(2) adrenergic antagonist, abrogated the stimulatory action of both clonidine and xylazine, but not the suppressive proliferative activity of xylazine in vitro. The inhibited proliferation of splenocytes to Con A correlated with increased apoptosis of T cells. The apoptosis was not blocked by yohimbine or antibodies to Fas and Fas-L. N-Nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, enhanced proliferation of splenocytes to Con A, partly abrogated the inhibitory effect of xylazine in the proliferation assay, and, only at high concentration (1000 microM), partly suppressed apoptosis of lymphocytes. The enhancing effect of L-NAME on the Con A-induced proliferation of splenocytes correlated with decreased NO production. However, decreased NO production observed in cultures with xylazine was followed by both decreased lymphocyte proliferation and apoptosis. Cumulatively, these results suggest that the immunosuppressive properties of xylazine on splenocytes in vitro are due to increased apoptosis of lymphocytes, predominantly involve NO-independent pathways, and are probably independent of its action through alpha(2) adrenoreceptors.

Comparison of signaling pathways involved in apoptosis of a thymocyte hybridoma triggered by a rat thymic medullary epithelial cell line, dexamethasone or T-cell receptor cross-linking.

Using an in vitro co-culture assay we found that a rat medullary thymic epithelial cell (TEC) line (TE-R2.5) induces apoptosis of the BWRT8 thymocyte hybridoma (TH) (CD4(hi)CD8(low) alphabetaTCR(hi)). TH apoptosis induced by this TEC line was predominantly mediated by direct cell-cell contacts and was potentiated by cross-linking of the T cell receptor (TCR) by R73 monoclonal antibody (mAb). Dexamethasone (Dx) also triggered TH apoptosis but inhibited death of these cells induced by TE-R2.5 cells or immobilized R73 mAb. The TEC-induced apoptosis was independent of the LFA-1/ICAM-1 interaction but partly depended on a novel 29 kDa molecule expressed on TE-R2.5 cells. All three types of TH apoptosis were followed by the cleavage of poly-(ADP-ribose)-polymerase and were blocked by a caspase inhibitor Z-Val-Ala-Asp(OMe)-CH(2)F.PKC stimulation by phorbol myristate acetate interfered with the TH apoptosis induced by TE-R2.5 and Dx, but did not modulate the effect of R73 mAb. On the contrary, inhibition of calcineurin with cyclosporine A did not influence the apoptosis induced by TE-R2.5 and Dx, but completely prevented the R73-triggered TH cell death. The TE-R2.5-mediated BWRT8 apoptosis was suppressed by Na-orthovanadate, an inhibitor of protein tyrosine phosphatases (PTP) as well as by genistein, a protein tyrosine kinase (PTK) inhibitor, while both compounds potentiated the effect of Dx. Blocking PTP, but not PTK decreased the proapoptotic effect of R73 mAb. These results, including those using a BWRT8 subclone (BWRT8-MDP.2) which is resistant to TCR-triggered apoptosis, but sensitive to apoptosis stimulated by TE-R2.5 and Dx, indicate that TE-R2.5-induced TH apoptosis in our model is different from apoptosis in other TEC co-culture models, published so far.

Modulatory effect of 7-thia-8-oxoguanosine on proliferation of rat thymocytes in vitro stimulated with concanavalin A.

7-thia-8-oxoguanosine (immunosine) is a guanosine analogue showing immunostimulatory activity on different components of the immune system, including B lymphocytes, natural killer cells and macrophages. However, little is known about its effect on T-cell functions. In this work it was demonstrated that immunosine at concentrations between 10 microM and 1 mM stimulated proliferation of rat thymocytes in vitro triggered by suboptimal concentrations of concanavalin A (Con A). The effect correlated with increased interleukin 2 (IL-2) production, upregulation of the IL-2 receptor alpha (IL-2Ralpha) expression and decreased apoptosis of thymocytes in comparison to the effect of Con A alone.

Xylazine, an alpha 2-adrenergic agonist, modulates proliferation of rat thymocytes in vivo and in vitro.

The effect of xylazine, an alpha 2-adrenergic agonist, on proliferation of rat thymocytes in vivo and in vitro was examined. It was found that the agonist administered to rats in vivo at doses of 2.5 mg/kg and 5 mg/kg stimulated thymocyte proliferation to suboptimal (0.625 microgram/ml) concentrations of concanavalin A (Con A). A similar effect was confirmed in vitro when lower concentrations of xylazine (5 microM) were added to cultures of thymic cells from intact animals in the presence of both suboptimal and optimal (2.5 micrograms/ml) Con A concentrations. Higher doses in vivo (25 mg/kg) and in vitro (50 microM, 100 microM and 250 microM) significantly inhibited proliferation of thymocytes to Con A. The phenomenon was followed by a decrease in interleukin-2 (IL-2) production (in vivo and in vitro) and down-regulation of IL-2 receptor alpha (IL-2R alpha) expression (in vitro). The exogenous IL-2 completely restored the inhibitory effect of xylazine in vivo on thymocyte proliferation. However, a minimal influence of the cytokine on the xylazine-inhibited thymocyte proliferation in vitro was observed. Stimulatory effect of xylazine on proliferation of thymocytes was probably mediated through alpha 2-adrenoreceptors since it was blocked by yohimbine, an alpha 2-adrenoreceptor antagonist. It seems that the pathways involved in inhibition of thymocyte proliferation by xylazine are more complex because the xylazine-suppressed thymocyte proliferation was potentiated by yohimbine.

The aging process--an analysis of the latent structure of body morphology (in males).

The morphological characteristics (20 anthropometric variables) of a total of 2,351 examinees (from the age of 18 to 90) were analyzed by a model of the principal components of the factor analysis. Four factors were extracted that explain 71.4% of the total variance. The factors-"general body voluminosity", "subcutaneous fat tissue", "longitudinal body dimensionality" and "upper body voluminosity"-were analyzed within the context of their appearance in different age-determined cohorts. The differences between cohorts (groups per ten years of age) were studied by the canonical discriminant analysis. The first two discriminant functions (describing mostly the variability of cohorts-96.11%) indicate a constant decrease of body and sitting height, and an increase of upper body voluminosity till the fourth age cohort, which is the most crucial one in the change of latent morphological structure. Results of the correct classification of cohort members show that only 48.45% of probands were correctly placed (the best classification determined was in the age between 46 and 55 years) indicating that in males, at least three different groups exist according to the specificity of morphological aging in human organisms.

Hemodynamic mechanisms of the effect of nitroglycerin in patients with acute myocardial infarction.

We studied the hemodynamic response to intravenous nitroglycerin (NTG) in 40 patients with and without acute heart failure (hemodynamic subsets I-IV) during acute myocardial infarction. Hemodynamic measurements were performed by right heart catheterization. The results showed that NTG response influenced mainly the preload and to a lesser extent the afterload, however these changes were dependent on initial hemodynamic status. The changes in mean arterial pressure and cardiac index were predominantly related to pretreatment pulmonary wedge pressure and slightly to systemic vascular resistance. Response to NTG could be predicted with 85% probability as a decrease of pulmonary wedge pressure, with 58% probability as a decrease in mean arterial pressure and cardiac index, and with 32% probability as an increase in cardiac index and a decrease in systemic vascular resistance. These results indicate that NTG therapy could have optimal results in patients with elevated pulmonary wedge pressure and normal cardiac index, while in the subsets with low mean arterial pressure or low cardiac index potentially deleterious decrease in these values could occur. Therefore the optimal condition for use of intravenous nitroglycerin in the patients with acute heart failure is isolated pulmonary congestion.

Intravenous isosorbide-5-mononitrate in the treatment of acute myocardial infarction.

The action of isorsorbide-5-mononitrate (IS-5-MN) infusion (range 6.0 to 10.0 mg/hour) was studied in 24 patients with and without acute heart failure (hemodynamic subsets I to IV) during acute myocardial infarction. Hemodynamic measurements were performed by right-sided cardiac catheterization. Intravenous IS-5-MN demonstrated significant hemodynamic effects compared with baseline values. In subsets I and II, a decrease in pulmonary wedge pressure (PWP) and in cardiac index (CI), without significant changes in heart rate, mean arterial pressure or systemic vascular resistance index were demonstrated. In subsets III and IV, a major increase in CI and a decrease in systemic vascular resistance index, as well as a decrease in PWP were found. Again no changes occurred in mean arterial pressure and heart rate. The dosage was similar in subsets I to IV (8.0, 7.9, 7.8 and 7.3 mg/hour); thus, the differences in the responses could not be attributed to dosage. It appears that several different patterns of hemodynamic IS-5-MN action exist, assuming that IS-5-MN operates on preload and afterload levels. The action of IS-5-MN mechanisms seems to be dependent on an initial hemodynamic subset. No patient had any deleterious hemodynamic effects. A decrease in CI in subsets I and II was not of clinical importance with these dosages. No nitrate tolerance during 9.0 hours of continuous therapy appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized placebo controlled, double-blind, crossover trial of transdermal nitroglycerin in stable angina pectoris.

Clinical efficacy of 5 mg per 24 hours transdermal nitroglycerin was studied in a placebo controlled, randomized, double-blind crossover trial, with three days wash-out period at the beginning, in 40 patients with chronic stable angina pectoris during two periods of 14 days. Assessment was carried out by means of a diary method, by the multistage treadmill exercise test, five hours after dosing, and by 24-hour ambulatory ECG recordings. Nitroglycerin patch demonstrated significant improvement of exercise tolerance comparing to placebo, in exercise time to the onset of angina pectoris and ST-segment depression of greater than or equal to 1.0 mm (+45% and +47%), in maximum walking time (+13%), as well as in diminished severity of maximum angina (-38%), in lower maximal ST-segment depression (-32%) and in faster recovery of ST-depression 3 and 6 minutes after the test (-28% and -44%). Nitroglycerin patch showed 33% less angina attacks, mainly severe and moderate, resulting in 37% less sublingual nitroglycerin consumption. A significant fall in the number of ST-segment depression episodes of 1.5 mm or more (-60%) was shown in the 24-hour ECG. All these changes were confirmed to be significant compared to placebo values, at a level of P less than 0.01, by multivariate analysis. This study revealed a positive effect of low dose nitroglycerin patch on improvement of exercise functional capacity and signs of myocardial ischaemia after 14 days of continuous therapy.

Acute and chronic efficacy of low-dose nitroglycerin patches in stable angina pectoris.

In a single-blind placebo controlled study, acute and chronic efficacy of low-dose nitroglycerin patches (NTG 5 mg/day) was studied in 24 patients with stable angina pectoris. NTG patch effects were evaluated by means of the multistage treadmill exercise test. During the acute study one exercise test was carried out after the wash-out period, after placebo patch (5 hours after application) and NTG patch (5, 16, 20 and 24 hours after application), so that a 3 day wash-out period had preceded each exercise test. Afterwards, chronic NTG patch therapy was continued for three months. At the end of this period exercise tests were carried out, in three day intervals of therapy, 5, 16, 20 and 24 hours after therapy. Then, a 7 day placebo patch period was continued with one exercise test at the end, 5 hours after application. Statistical analysis was carried out by multivariate analysis of difference. Systolic and diastolic blood pressure at rest fell significantly only in the acute 5 hour measurement, with no change in the other periods. The NTG patch augmented significantly mainly all heart rate values during exercise test, with no change in resting values. Placebo, acute and chronic exercise tests did not show any significant difference. They showed a slight but significant placebo influence on the exercise test compared to the wash-out period, improving maximum walking time and time to the onset of angina pectoris but with worsening of maximum ST-depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Different hemodynamic actions of trinitroglycerin and isosorbide dinitrate in patients with acute myocardial infarction.

The hemodynamic effects of intravenously administered trinitroglycerin (TNT) and isosorbide dinitrate (ISDN) in stechiometric equivalent doses were studied in 30 patients with acute myocardial infarction. Both drugs were given over 30 min in every patient, and the stability of the condition of the patient was checked by administering the initial drug again. Measurements were made by right heart catheterization using a balloon tip thermodilution catheter and a catheter in the radial artery. TNT and ISDN have different hemodynamic effects. By multivariate analysis it could be shown that TNT is a venous dilator, lowering mainly pulmonary capillary pressure, while ISDN acts more as a mixed vasodilator, diminishing mainly peripheral vascular resistance and increasing cardiac output. These drugs have, therefore, a different spectrum of indications in patients with acute myocardial infarction.

[Hemodynamic effects of intravenous isosorbide dinitrate in acute myocardial infarct]. / Effets hémodynamiques du dinitrate d'isosorbide intraveineux dans l'infarctus myocardique aigu.

The hemodynamic effects of intravenous isosorbiddinitrate (ISDN) were studied in 15 patients with acute myocardial infarction. Pressure and flow parameters were measured by right heart and radial catheterization and by the thermodilution method. 3-9 mg/hour ISDN was infused intravenously and the hemodynamic values were measured during half an hour in clinically stable state. The statistical analysis was carried out by paired Student's t-test and factors analysis. After ISDN therapy 10 patients showed a significant fall in pulmonary capillary pressure (-24%), 9 a rise in stroke volume index (+21%) and cardiac index (+13%). Two patients only exhibited a rise in pulmonary capillary pressure (+10%) and one a fall in cardiac index (-5%). ISDN changes in pulmonary capillary pressure, stroke volume and cardiac output were mainly due to changes in pulmonary and systemic vascular resistances and much less to those in the systemic venous bed. It can be supposed that intravenous ISDN behaves more like a mixed than a venous vasodilator and can be recommended for acute myocardial infarction patients with high pulmonary capillary pressure and low cardiac output.