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Biomedical subjects

J Enns

Publications and source records attributed to J Enns.

10 recordsLinked to original sources
PubMed1996

Cyclosporine inhibition of leukocyte calcineurin is much less in whole blood than in culture medium.

Recent reports have shown that cyclosporine (CsA)-treated patients have abundant calcineurin phosphatase (CN) activity in vivo despite CsA blood concentrations that would be completely inhibitory in vitro. We sought to determine whether this disparity was a result of altered distribution of CsA in culture medium (CM) compared with whole blood (WB). CN activity was measured in peripheral blood leukocytes (PBL) that had been exposed in vitro to CsA in either WB or CM. Cells from both groups were also stimulated with OKT3 to determine the effect of CsA on the induction of IFN-gamma synthesis. CsA accumulation in PBL was determined by liquid scintillation counting of PBL exposed to 3H-CsA. The IC50 for CsA inhibition of CN activity was significantly lower for PBL in CM (2 micrograms/L) compared with PBL in WB (102 micrograms/L, P < or = 0.005). Likewise, for CsA inhibition of IFN-gamma induction, the IC50 was 18 micrograms/L for PBL in CM compared with 690 micrograms/L for PBL in WB (P < or = 0.005). The shift in IC50 was accompanied by a 10-fold increase in 3H-CsA in PBL in CM compared with PBL in WB. We conclude that PBL exposed to CsA in CM accumulate significantly more CsA than PBL in WB. The result is that CsA inhibition of CN activity and cytokine induction appears at least an order of magnitude greater than its true effect in biologic fluids. This disparity is due to partitioning of CsA to irrelevant CsA binding sites, which are abundant in WB and in vivo, but absent in culture medium.

Calcineurin↗
PubMed1996

The functional consequences of partial calcineurin inhibition in human peripheral blood mononuclear leucocytes.

Calcium-dependent signal transduction is essential to the induction of cytokine expression by stimuli acting through the T cell receptor. In vitro, the immunosuppressant cyclosporine (CyA) blocks this pathway by inhibition of calcineurin (CN) phosphatase activity. But in vivo, patients on CyA have only 50% inhibition of CN and can mount cytokine responses. To simulate this state of partial inhibition, we studied the responses of human peripheral blood mononuclear leucocytes (PBL) in vitro at low CyA concentrations. PBL were challenged in vitro with calcium ionophores or anti-CD3 monoclonal antibody. The induction of IFN-gamma (interferon-gamma) and IL-2 (interleukin 2) steady-state mRNA was studied by Northern blotting and reverse transcriptase-polymerase chain reaction. IFN-gamma was assessed in a radiolabelled antibody binding assay or by ELISA (enzyme-linked immunosorbent assay). CN was assessed by dephosphorylation of a 32P-serine labelled 19 amino acid substrate. CyA inhibited CN with an IC50 (concentration giving 50% inhibition) of 10 ng/ml (95% confidence interval, CI = 8-13 ng/ml). Likewise, the induction of IFN-gamma and IL-2 mRNA by calcium ionophore A23187 was inhibited with IC50 of 14 ng/ml (95% CI = 8-27 ng/ml) and 32 ng/ml (95% CI = 5-178 ng/ml), respectively, while the IC50 for inhibition of IFN-gamma protein secretion was 8 ng/ml (95% CI = 9-18 ng/ml). Partial inhibition of CN also altered the threshold for IFN-gamma induction. CyA 10 ng/ml inhibited IFN-gamma induction by anti-CD3 monoclonal antibody OKT3 significantly more at low OKT3 concentrations (10 ng/ml, mean +/- SEM = 72 +/- 9% inhibition) compared to high OKT3 concentrations (1000 ng/ml, 47 +/- 6%, p < 0.01). Similar results were seen using high and low concentrations of A23187. Finally, cells pretreated with CyA recovered the ability to respond to high concentrations of A23187 (5 microM) faster than low concentrations (0.5 microM). We conclude that the principal defect in lymphocytes with partial CN inhibition is a reduction in maximum cytokine output which is closely related to the degree of CN inhibition. In addition, there is significantly greater inhibition of weak stimuli compared to maximal stimuli. These defects may explain why patients on CyA can have a reduction in immune responsiveness but still retain protection from infection.

Blotting, Northern↗
PubMed1995

Cyclosporine inhibition of calcineurin activity in human leukocytes in vivo is rapidly reversible.

Despite increasing information about the mechanism of action of cyclosporine A (CsA), little is known about the way lymphocytes recover from CsA. Recovery is central to understanding the pharmacodynamics of CsA in vivo. We studied the recovery of calcineurin phosphatase (CN) activity in CsA-treated cells. Single dose kinetics in renal transplant patients showed that inhibition of CN activity in PBL increased and fell concomitant with CsA blood vessels. In vitro, control PBL treated with CsA 100 micrograms/l, washed, and resuspended in CsA-free medium showed little recovery (0-20%) after 24 h. Erythrocytes or anti-CsA Ab added to the recovery medium increased recovery to 50% within 4 h. Similar recovery was seen in the ability of cells to produce IFN-gamma after OKT3 stimulation. Recovery of CN activity was associated with the efflux of [3H]CsA, was not blocked by cycloheximide and was temperature sensitive. A cell line with high expression of surface P glycoprotein (PGP), showed rapid recovery. However, PGP blockade did not prevent recovery in PBL, indicating a different PGP-independent mechanism. In PBL, recovery from CsA is slow and limited in vitro, but rapid in vivo, where CsA equilibrates among a complex set of extralymphocytic binding sites.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Effects of routine premedication for cardiac catheterization on sedation, level of anxiety and arterial oxygen saturation.

OBJECTIVE: To assess the efficacy and side effects of routine premedication in patients undergoing cardiac catheterization procedures in a tertiary cardiac care institute. The criteria used included: arterial hemoglobin oxygen saturation (%SaO2), level of sedation and level of anxiety before and after the procedure. Overall patient satisfaction was also quantified. DESIGN: Sixty-two adult patients scheduled for cardiac catheterization procedures were recruited for the study. They were premedicated with one of several premedication regimens: oral diazepam 5 to 10 mg; oral lorazepam 1 mg; oral diazepam 10 mg+oral promethazine 25 mg; or oral diazepam 10 mg+oral diphenhydramine 25 mg. No attempt was made to control the premedication the patients received; it was ordered by each patient's cardiologist according to personal preference. Patients underwent pulse oximetry and evaluation of sedation, anxiety and level of satisfaction before and after cardiac catheterization. RESULTS: All patients tested had values for mean precatheterization %SaO2 above 92%. No patient had postcatheterization %SaO2 readings below that defined as indicating clinically significant hypoxemia (%SaO2 less than 90%). Patients were awake or lightly sedated before and after cardiac catheterization. Thirteen per cent of patients suffered from high levels of anxiety before, and 16% during, cardiac catheterization. Twenty-three per cent of patients reported being dissatisfied with the premedication before, and 10% of patients reported being dissatisfied during, cardiac catheterization. CONCLUSIONS: Clinically significant hypoxemia and oversedation are not problems for most patients given the types and doses of precatheterization medication used in the study population. The premedication schedules followed in the study failed to provide satisfaction and anxiolysis in a significant number of those studied.

Aged↗
PubMed1992

The responsiveness of cerebral blood flow to changes in arterial carbon dioxide is maintained during propofol-nitrous oxide anesthesia in humans.

Because it is common to manipulate PaCO2 during neurosurgery, it is essential to characterize the relationship between cerebral blood flow (CBF) and changes in PaCO2. The purpose of this study was to investigate the effects of propofol-N2O anesthesia on the CBF response to changes in PaCO2 in healthy subjects. In seven patients, anesthesia was induced with propofol 2.0-2.5 mg/kg and then maintained with a propofol infusion of 12 mg.kg-1.h-1 for 10 min and then 9 mg.kg-1.h-1 for 10 min and then was reduced to 3-6 mg.kg-1.h-1 for the remainder of the study. The subjects' lungs were ventilated with N2O in O2 (FIO2 0.3) to the end-tidal CO2 present before anesthesia, and then CBF was measured using intravenous 133Xe and ten scintillation counters, five over each cerebral hemisphere. ETCO2 then was increased to 50 mmHg and CBF measurement repeated; ETCO2 then was reduced to 30 mmHg and CBF measurement repeated. Concurrent with each CBF measurement, arterial blood was sampled for PaCO2 and hemoglobin measurement. CBF at normocapnia (PaCO2 42 +/- 2 mmHg) was 33 +/- 7 ml.100 g-1.min-1, which increased to 58 +/- 10 ml.100 g-1.min-1 and decreased to 19 +/- 4 ml.100 g-1.min-1 on increasing PaCO2 (53 +/- 4 mmHg) and decreasing PaCO2 (31 +/- 2 mmHg), respectively. Both the PaCO2 and CBF values were statistically different from those measured at any other time (CBF P less than 0.002, PaCO2 P less than 0.001). The slope of CBF versus PaCO2 was 1.56 ml.100 g-1.min-1.mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Repair of a false aneurysm of the aortic arch.

A 66-year-old man having previously undergone repair of aneurysms of the ascending, transverse and infrarenal aorta, presented with a large false aneurysm of the aortic arch. Successful repair of the aneurysm was achieved under a state of profound hypothermia and circulatory arrest. The patient remains well and free from aortic aneurysmal disease two years after surgery.

Aged↗
PubMed1983

Prehospital cardiac rhythm deterioration in a system providing only basic life support.

Access to an ambulance service trained to provide only basic cardiac life support (BCLS) and adjunctive ventilation with oxygen provided the opportunity to study cardiac rhythms during BCLS in patients with circulatory arrest. Holter monitoring was attempted in 43 patients. Technically adequate traces throughout transport to hospital were obtained in 21. The average monitored time was 11.9 minutes. A tachydysrhythmia (mainly VF/VT) was initially found in 10, heart block or bradycardia in 9, and asystole in 2 persons. During BCLS, six patients with bradycardic rhythms converted temporarily to VF. The first ECG tracing obtained in the hospital revealed, however, that only five were still in a tachydysrhythmia and 15 were asystolic. These data demonstrate that important rhythm changes occur when BCLS is continued for several minutes during circulatory arrest. Although some bradycardic rhythms convert to VF, the VF is not sustained. After an average of 12 minutes, 90% of those initially in bradycardic rhythm and 50% of those initially in VF/VT were asystolic. This study provides further evidence that BCLS does not prevent cardiac deterioration.

Ambulances↗
PubMed1982

Pre-hospital analgesia with Entonox.

Pre-hospital self-administered analgesia using a 50:50 mixture of nitrous oxide and oxygen (Entonox) was evaluated in 240 patients. Of these, 93.4 per cent experienced either complete or partial relief from traumatic, chest, abdominal or back pain. Drowsiness was the most common side effect noted. No complications occurred during delivery of the mixture. Attention is drawn to the effect of extreme temperatures on the Entonox mixture and recommendations are made with respect to its use below-freezing climates. Because of its ease of use and short duration of action, Entonox appears to be well suited for the treatment of pre-hospital pain by Emergency Medical Technicians.

Adolescent↗