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S Nagy

Publications and source records attributed to S Nagy.

At least 73 records · Page 4Linked to original sources
PubMed1994

Role of histamine in the intestinal flow response following mesenteric ischemia.

Sudden reperfusion of the gut following prolonged ischemia can itself have more deleterious consequences than the ischemia alone. Studies of vasodilator factors influencing the increased flow on reperfusion are therefore of importance. In the present study, a possible role of histamine in the postischemic flow response was examined after a period of total segmental ischemia. The artery supplying the terminal ileum was occluded in anesthetized dogs. Ischemia of 30 min duration was followed by a 30 min reperfusion period (control postischemic flow response), and the arterial blood flow to the segment was measured. After the control postischemic flow response, one of the following drugs was administered intravenously: histamine H1-or H2-blockers (tripelennamine, .5 mg/kg, cimetidine, 10 mg/kg, ranitidine, 2 mg/kg), cromolyn (a mast cell stabilizer, 25 mg/kg), and aminoguanidine (a diamine oxidase blocker, 50 mg/kg). The 30 min ischemia-30 min reperfusion cycle was then repeated (test postischemic flow response). A 30 min mesenteric ischemia-reperfusion period is reproducible once without a significant change in its hemodynamic parameters. The duration and volume of the postischemic flow response were significantly decreased by cimetidine, ranitidine, or cromolyn, and were increased by aminoguanidine. Tripelennamine did not affect the postischemic vasodilator response. At the onset of reperfusion, a release of endogenous histamine occurs from the gut, originating mainly from mast cells. It is proposed that histamine participates in the postischemic flow response through the H2-receptors.

Animals↗
PubMed1994

Histamine release and its effects in ischaemia-reperfusion injury of the isolated rat heart.

Histamine is released from the heart during ischaemia-reperfusion injury. As histamine has cardiac effects, we investigated the role of histamine in ischaemia-reperfusion injury of isolated rat hearts. A Langendorff-model with 30 min global (37 degrees C) ischaemia followed by 60 min reperfusion was employed. The effects of ischaemia alone (n = 10, group 1.1 + n = 10, group 2.1, 2 different series), and ischaemia with H1- and H2-receptor blockade with cimetidine (10 microM, n = 10), chlorpheniramine (10 microM, n = 8), terfenadine (10 microM, n = 8), and promethazin (10 microM, n = 9), or both cimetidine and chlorpheniramine (n = 8), were studied. Histamine was measured in the coronary effluent and cardiac tissue of group 1.1. Release of histamine increased from 6.5 +/- 1 pmol min-1 before ischaemia to 19 +/- 3 pmol min-1 at the start of reperfusion. Ischaemia decreased left ventricular developed pressure to 18 +/- 11% (1.1) and 50 +/- 11% (2.1) of initial value (mean +/- SEM) at the start of reperfusion. Left ventricular end-diastolic pressure increased from 0 to 79 +/- 8 mmHg (1.1) and 39 +/- 9 (2.1) mmHg, while left ventricular systolic pressure was unchanged (101 +/- 12% in 1.1 and 101 +/- 10% in 2.1). Severe arrhythmias were induced in 90 (1.1) and 30 (2.1)% of the hearts, while coronary flow decreased during reperfusion. H2-blockade did not modify the changes in left ventricular pressures, coronary flow, or heart rate induced by ischaemia. Three different H1-blockers increased left ventricular systolic pressure, inhibited the decrease of developed pressure, attenuated the increase of end-diastolic pressure, and totally inhibited reperfusion arrhythmias. The effect of both blockers together was similar to that of H1-blockers alone. Coronary flow was increased during reperfusion in two of the groups with H1-blocker compared with ischaemic controls. Increased release of histamine from ischaemic-reperfused rat hearts concurred with depression of left ventricular function and arrhythmias during early reperfusion. Cardiac dysfunction during reperfusion was attenuated by three different H1-receptor blockers.

Animals↗
PubMed1994

Intramucosal pH changes following complete segmental small intestinal ischemia, as compared with the effects of superior mesenteric artery occlusion.

Microcirculatory nonperfusion of the intestinal mucosa may result in a subsequent prolongation of tissue ischemia, even after restoration of the mesenteric blood flow. It was hypothesized that there is a relationship between mucosal no-reflow and the amount of previously ischemic tissues during intestinal ischemia reperfusion. Accordingly, an examination was made of the changes in intestinal and gastric intramucosal pH (pHi) in dogs after a 120-min complete occlusion of the superior mesenteric artery (SMA) and those observed following ischemia of an ileal segment only. pHi, as an indicator of the adequacy of mucosal microcirculatory perfusion, was calculated by the tonometer technique. Baseline values of intestinal pHi (mean 7.25 +/- 0.12) and gastric pHi (mean 7.23 +/- 0.27) were determined in sham-operated animals. The 120-min intestinal ischemia caused a progressive fall in intestinal pHi to a mean value of approximately 6.8. Reperfusion resulted in a slow return to nearly normal pHi levels in the ileal segment, but essentially no intestinal pHi elevation was observed during the 90-min period following occlusion of the SMA. The gastric pHi remained at the control level during segmental intestinal ischemia reperfusion, but declined below the normal range following release of the occlusion of the SMA. It is proposed that continuing microcirculatory nonperfusion could explain the failure to demonstrate a postreperfusion elevation of pHi following complete occlusion of the SMA.

Animals↗
PubMed1994

The measurement of cardiac output in dogs by impedance cardiography with different electrode arrangements.

This study was performed to compare cardiac output (CO) values determined by means of impedance cardiography (ICG) with the conventional four-band electrode array and with different spot electrode arrays in anaesthetised dogs. CO values determined at end-expiratory apnoea with hand-calculation (ICG1) and during several respiratory cycles with a computer program (ICG2) were compared with values obtained via simultaneous thermodilution (TD) measurements. Changes in CO during isoproterenol infusion, bleeding and reinfusion were also studied by means of ICG1, using one of the spot electrode arrays and TD. Band voltage electrodes yielded a significantly lower CO, whereas spot electrodes on the left thorax gave a significantly higher CO than that measured with TD. In spite of the high correlation coefficients in the different electrodes arrays, the bias between ICG1 and TD, and that between ICG2 and TD CO in the SL1-SL8 and BN-BX electrode arrays showed differences statistically significant from zero. The percentage changes in CO measured with ICG1 in the SN-SX electrode array and TD during isoproterenol infusion, bleeding and reinfusion also showed a high correlation. These results indicate that band voltage electrodes can be replaced by the more convenient spot electrodes in certain arrays. Further CO may be measured during several respiratory cycles by using a computer program. Thus, ICG is a reproducible, non-invasive method for the measurement of CO in anaesthetised dogs.

Animals↗
PubMed1994

Adolescent sexual activity in Alabama.

OBJECTIVE: Early adolescent sexuality has reached epidemic proportions in the US. Most investigations on adolescent sexuality have focused on large urban populations. The objective of this study was to identify the rate of adolescent sexuality in a Southern population and make comparisons to national studies. METHODS: Data were collected by surveying 3370 students in the eighth and tenth grades from across the state of Alabama. The survey utilized was a modified version of the Alabama Adolescent Student Health Survey, an instrument derived from the National Adolescent Student Health Survey. RESULTS: The male sexual experience rate was 41% compared to the female rate of 39%. Tenth graders (44%) were more sexually experienced than eighth graders (37%). Blacks (50%) were more sexually active than whites (35%). Adolescents from single parent (45%) or non-parent households (46%) were more likely to be sexually active than those from two-parent households (36%). CONCLUSIONS: The rates of reported sexual activity in this survey are alarming and are similar to rates reported in the literature. This study helps document the increasing rate of sexual activity as teenagers span the adolescent years. Family physicians are in an ideal position to help educate adolescents about risky sexual behaviors.

Adolescent↗
PubMed1994

A comparison of risky health behaviors of sexually active, sexually abused, and abstaining adolescents.

OBJECTIVE: To report on rates of sexual abuse among a normative sample of adolescents and identify psychosocial correlates associated with sexual abuse. METHOD: An anonymous self-report survey examining an array of psychosocial items to which 3448 grade 8 and 10 students from rural and metropolitan school districts in a southern state responded. RESULTS: There was a 105 rate of sexual abuse among this normative sample. Victims of forced sex were disproportionately female and African-American, and were more likely to reside in single-parent households. These sexually abused girls reported significantly higher levels of risky health behaviors and risky attitudes on 11 (P < .001) of the 12 comparisons. Sexually abused boys showed a similar pattern on eight (P < .001) comparisons. CONCLUSIONS: Indications are that forced sex experiences are associated strongly with risky health behaviors in some adolescents, which should alert clinicians to the possibility of sexual abuse.

Adolescent↗
PubMed1993

[Fetal chromosome abnormalities diagnosed by chorionic villi sampling].

Chorionic villus sampling was performed for chromosome analysis in 387 cases during a 4-year-period. In 115 cases transcervical while in 272 cases transabdominal sampling was carried out. Chromosomal abnormalities were found in 25 cases (6.4%). Autosomal trisomies occurred in 17 cases, structural anomalies in 2 cases and sex chromosomal aberrations in 6 cases. The pregnancy was terminated in 19 cases because of chromosome abnormality, in 5 further cases because of X-linked disease and male fetus. After transcervical sampling spontaneous abortion occurred in 7 cases (5.8%), while after transabdominal sampling in 8 cases (2.8%). The authors prefer in their practice the early transabdominal CVS, which can be performed safety already at the end of the first trimester.

Chorionic Villi Sampling↗
PubMed1993

Toxic oxygen metabolites and ischemia-reperfusion increase histamine synthesis and release in the isolated rat heart.

Histamine is synthetized in the heart, and released by ischemia-reperfusion injury in several species. Histamine has arrhythmogenic, chronotropic, inotropic and vasoactive effects. Cardiac histamine release during ischemia-reperfusion may be mediated by toxic oxygen metabolites. We studied the effect of ischemia-reperfusion and toxic oxygen metabolites on release and synthesis of histamine in the isolated rat heart (Langendorff model). The following groups were included: I, (n = 10) control perfusion for 60 min; II, (n = 7) H2O2 (200 microM) was given for 10 min followed by 50 min recovery; III, (n = 7) thiourea (15 mM) was given in addition to H2O2; IV, (n = 7) thiourea given alone; V, (n = 7) catalase (150 U/ml) plus H2O2; VI, (n = 7) 20 min ischemia followed by 40 min reperfusion. The contents of histamine in the coronary effluent and in cardiac tissue were measured repeatedly (radioenzymatic method). Ischemia-reperfusion and toxic oxygen metabolites increased release of histamine in the coronary effluent. Concomitantly the histamine contents in cardiac tissue increased, indicating increased synthesis of histamine.

Animals↗
PubMed1993

Release of histamine from isolated rat hearts during reperfusion is not dependent on length of ischemic insult, or contents of histamine in cardiac tissue.

Release of histamine (H) by ischemia-reperfusion injury was investigated in isolated rat hearts (Langendorff model). The effect of 10, 15, 20, 25, 30, 40 and 60 min ischemia (n = 10 each) on H in the coronary effluent and in cardiac tissue was studied after 4 min reperfusion. Release of creatine kinase and lactate dehydrogenase in the coronary effluent increased with time of ischemia. Tissue H increased from 95 +/- 10 ng/g rat heart (mean +/- SEM) before ischemia to max 148 +/- 10 ng/g after 20 min ischemia (p < 0.002), and increased also after 15 (p < 0.01), 25 (p < 0.01), and 30 min (p < 0.045). H in the coronary effluent increased after 15 (from 16 +/- 3 to 26 +/- 2 pmol/min, p < 0.044), 30 (26 +/- 6 pmol/min, p < 0.027), and 60 min ischemia (47 +/- 6 pmol/min, p < 0.0044). Release of H during ischemia-reperfusion is neither dependent on the severity of the ischemic insult, nor on the level of tissue H.

Animals↗
PubMed1993

Reperfusion mucosal damage after complete intestinal ischemia in the dog: the effects of antioxidant and phospholipase A2 inhibitor therapy.

In a recent study, reperfusion mucosal injury was demonstrated in a rat model of total ischemia if venous congestion was avoided. The aims were to examine the possibility of reperfusion damage in a canine model involving 2 hours of complete segmental ischemia and to investigate the effects of antioxidant therapy or pretreatment with nonspecific phospholipase A2 inhibitors on postocclusive mucosal changes. Tissue samples were evaluated histologically in a blind manner, according to a 0 to V grade scale. The degree of mucosal damage was statistically significantly increased during the 30-minute reperfusion period. Similarly, 2 hours of total ischemia followed by 30 minutes of reperfusion produced significantly more tissue lesions than did 2 1/2 hours of ischemia without reperfusion. Oral allopurinol pretreatment supplemented by an intravenous dose, or oral allopurinol in combination with a superoxide radical scavenger, resulted in a significant amelioration of postischemic histologic changes. Pretreatment with a nonspecific phospholipase A2 inhibitor (methylprednisolone, dexamethasone, or quinacrine) was ineffective in diminishing the reperfusion injury in either case. The results suggest that reperfusion injury may develop even after complete intestinal ischemia, and this damage can be attenuated by inhibiting the capacity of xanthine oxidase to generate reactive oxygen intermediates.

Allopurinol↗
PubMed1992

Input impedance and peripheral inhomogeneity of dog lungs.

Tracheal pressure, central airflow, and alveolar capsule pressures in cardiac lobes were measured in open-chest dogs during 0.1- to 20-Hz pseudorandom forced oscillations applied at the airway opening. In the interval 0.1-4.15 Hz, the input impedance data were fitted by four-parameter models including frequency-independent airway resistance and inertance and tissue parts featuring a marked negative frequency dependence of resistance and a slight elevation of elastance with frequency. The models gave good fits both in the control state and during histamine infusion. At the same time, the regional transfer impedances (alveolar pressure-to-central airflow ratios) showed intralobar and interlobar variabilities of similar degrees, which increased with frequency and were exaggerated during histamine infusion. Results of simulation studies based on a lung model consisting of a central airway and a number of peripheral units with airway and tissue parameters that were given independent wide distributions were in agreement with the experimental findings and showed that even an extremely inhomogeneous lung structure can produce virtually homogeneous mechanical behavior at the input.

Airway Resistance↗
PubMed1992

Longitudinal examination of teachers' burnout in a school district.

Teachers in a rural school district were administered the Maslach Burnout Inventory three times over a five-year period. Teachers scoring high on emotional exhaustion and low on personal accomplishment were classified as "experiencing burnout." Across the three waves, the proportion of teachers meeting these criteria for burnout were 7%, 11%, and 11%, respectively. By grade, burnout was noted among 3%, 8%, and 9%, respectively, over time for senior high-school teachers; 7%, 7%, and 11% for junior high-school teachers; and 9%, 17%, and 12% for elementary school teachers. Interventions must consider grade-taught and are probably most cost-effective for elementary school. It is important to establish norms across time and across school settings to determine high-risk groups deserving interventions.

Alabama↗
PubMed1992

Effects of FK506 and cyclosporin A on cytokine production studied in vitro at a single-cell level.

Mononuclear cells obtained from human blood were mitogen or antigen activated in vitro in the presence or absence of FK506 or cyclosporin A (CsA). Cytokine production was studied at a single-cell level by ultraviolet (UV) microscopy of fixed permeabilized cells using cytokine-specific monoclonal antibodies (mAb). Phenotypic characterization of the monokine-producing cells was achieved by two-colour immunofluorescent staining. Cytokine production after antigen activation with Staphylococcus aureus enterotoxin A (SEA) was significantly reduced. FK506 or CsA inhibited SEA-induced tumour necrosis factor-alpha (TNF-alpha) production both in monocytes (P less than 0.01) and in lymphocytes (P less than 0.001), at a drug concentration of 1-25 ng/ml for FK506 and 100-500 ng/ml for CsA. Lymphocyte synthesis of interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and TNF-beta after SEA activation was also significantly reduced by either of the drugs. In contrast, endotoxin-induced monokine production (TNF-alpha and IL-6) after lipopolysaccharide (LPS) stimulation was unaffected by FK506 or CsA even when added in concentrations as high as 1000 ng/ml. When the cells were stimulated by phorbol ester (phorbol 12-myristate 13-acetate, PMA) plus calcium ionophore (ionomycin), FK506 and CsA inhibited, in a dose-dependent manner, the production of IL-2, IL-4, IL-5, IFN-gamma and TNF-alpha. The 50% inhibitory concentration (IC50) for FK506 or CsA on the cellular synthesis of the various cytokines varied between 0.6 and 1.0 ng/ml and 20 and 60 ng/ml, respectively. Further stimulation by addition of anti-CD28 mAb to the cultures resulted in an augmented IL-2 and IFN-gamma production which was resistant to both FK506 and CsA. This report delineates extensive similarities between the two drugs in mechanisms of immunosuppression by blockade of identical interleukin production. Depending on the mode of cell activation the two drugs inhibited not only cytokine production in lymphocytes but also antigen-induced monokine (TNF-alpha) production in macrophages, although the optimal immunomodulatory effect of FK506 was achieved at a concentration approximately 50-fold lower than that of CsA.

Antigens, CD↗
PubMed1992

Studies on the relationship between xanthine oxidase and histamine release during intestinal ischemia-reperfusion.

Recent studies have demonstrated a connection between xanthine oxidase-generated reactive oxygen intermediates and histamine release during ischemia-reperfusion. In the present work, the effect of modulation of the endogenous histamine level on the xanthine oxidase activity was examined during the reperfusion of a canine ileal segment following a 2 hr of complete ischemia. The xanthine oxidase activity and the plasma histamine level peaked simultaneously at the beginning of reperfusion, reaching mean values of 14.9 nmol/ml/min and 12.1 nmol/l, respectively. Pretreatment with aminoguanidine, a blocker of diamine oxidase (histaminase), resulted in significantly higher levels of histamine during reperfusion, but this elevation was not accompanied by a further increase in xanthine oxidase activity. Pretreatment with the mast cell stabilizer cromolyn significantly diminished the rise in plasma histamine level, with an unchanging activity of xanthine oxidase. No significant alteration could be observed in the postocclusive activity of xanthine oxidase following the intra-arterial administration of 0.5, 1, or 5 nmol of histamine during the last 10 min of the ischemic period. These data suggest that the amount of histamine liberated during reperfusion does not result in a further increase in the xanthine oxidase activity. The release of histamine is not a cause, but rather an effect of the elevated activity of intestinal xanthine oxidase.

Animals↗
PubMed1991

Nonlinearity and harmonic distortion of dog lungs measured by low-frequency forced oscillations.

The nonlinearity of lung tissues and airways was studied in six anesthetized and paralyzed open-chest dogs by means of 0.1-Hz sinusoidal volume forcing at mean transpulmonary pressures (Ptp) of 5 and 10 cmH2O. Lung resistance (RL) and elastance (EL) were determined in a 32-fold range (15-460 ml) of tidal volume (VT), both by means of spectrum analysis at the fundamental frequency and with conventional time-domain techniques. Alveolar capsules were used to separate the tissue and airway properties. A very small amplitude dependence was found: with increasing VT, the frequency-domain estimates of RL decreased by 5.3 and 14%, whereas EL decreased by 20 and 22% at Ptp = 5 and 10 cmH2O, respectively. The VT dependences of the time-domain estimates of RL were higher: 10.5 and 20% at Ptp = 5 and 10 cmH2O, respectively, whereas EL remained the same. The airway resistance increased moderately with flow amplitude and was smaller at the higher Ptp level. Analysis of the harmonic distortions of airway opening pressure and the alveolar pressures indicated that nonlinear harmonic production is moderate even at the highest VT and that VT dependence is homogeneous throughout the tissues. In three other dogs it was demonstrated that VT dependences of RL and EL were similar in situ and in isolated lungs at both Ptp levels.

Airway Resistance↗
PubMed1991

Effect of antioxidant therapy on cyclooxygenase-derived eicosanoid release during intestinal ischemia-reperfusion.

Conflicting data have been reported on the relationship between reactive oxygen intermediates and the formation of oxygenase-derived eicosanoids. Plasma levels of prostacyclin (PGI2, measured as the stable metabolite 6-keto-PGF1 alpha) and thromboxane A2 (TxA2, measured as TxB2) in the effluent blood of a canine ileal segment were determined following 1 or 2 h of ischemia. The synthesis of both eicosanoids was significantly stimulated during reperfusion, but extension of the ischemic interval from 60 to 120 min was not followed by a further increase. The role of oxidants potentially involved in the process was investigated by using materials that inactivate the xanthine-oxidase-generated intermediates. Previous studies on the same in vivo animal model had demonstrated the effectiveness of antioxidant therapy in reducing the postischemic histamine release. There was no significant alteration in the amount of eicosanoids synthesized following oral allopurinol, catalase, dimethylsulfoxide, mannitol or desferrioxamine treatment. Intravenously administered allopurinol, however, significantly elevated the postischemic 6-keto-PGF1 alpha/TxB2 ratio. The results suggest that these antioxidants at doses inhibitory to histamine liberation are not effective in influencing the postischemic eicosanoid release. Intravenously administered allopurinol could exert a potentially beneficial effect through a mechanism other than the blockade of xanthine oxidase.

Allopurinol↗