CD4+ and CD8+ lymphocyte and cortisol response patterns in elderly and young males after methylprednisolone exposure

The elderly have impaired cellular immunity and are more predisposed to opportunistic infections after long term glucocorticoid treatment. No data, examining the response of lymphocyte subsets (CD4+, CD8+) under baseline conditions and after exposure to methylprednisolone in young and elderly males, are available. This crossover study examined lymphocyte subsets and cortisol response patterns in seven elderly males (66-82 years) and five young males (24-37 years) randomized into Phase I (24 hr baseline) and Phase II (10 mg intravenous dose of methylprednisolone). Whole blood samples were obtained at 0, 4, 8, 12 and 24 hr to determine total lymphocytes and CD4+ and CD8+ cells utilizing monoclonal antibodies and flow cytometry. The absolute number of lymphocyte subsets and the lymphocyte area under the time curve (AUC) were measured and a 12 and 24 hr lymphocyte response ratio (AUC Phase II divided by AUC Phase I) was determined. Serial plasma samples over 24 hours were collected to quantitate cortisol (Phase I) and methylprednisolone concurrent with cortisol (Phase II). Pharmacokinetic parameters were generated and the cortisol AUC was determined. The AUC values for lymphocytes and cortisol from Phase II quantitated the pharmacologic response to methylprednisolone exposure while Phase I data described the interpatient variability in these parameters. Diurnal patterns for lymphocytes and cortisol were noted in all subjects during Phase I. The mean CD4+ and CD8+ lymphocyte AUC from 0 to 24 hr during Phase I was significantly smaller for the elderly when compared to young men. However, after exposure to methylprednisolone, lymphopenia occurred in all subjects with a mean decline of 54% in the elderly and 60% (p = 0.44) in young subjects for the total lymphocyte count and returned to baseline by 8-12 hr. During Phase II, the CD4+ lymphocytes (72% decline in elderly; 70% in young; p = 0.71) demonstrated a more notable decline than CD8+ cells (44% decline in elderly; 52% in young; p = 0.31) with a nadir occurring between 4 to 6 hr for both subsets. The lymphocyte response ratio was not significantly different between groups for total, CD4+, and CD8+ cells at 12 hr or 24 hr determinations. A slower clearance of methylprednisolone was noted in the elderly (mean: 256 mL/hr/Kg) than in the young men (mean: 359 mL/hr/Kg; p < 0.05) during Phase II with no significant difference found between groups for volume of distribution, elimination rate constant or half-life. A significantly smaller cortisol suppression ratio [0.36+/-0.11 (elderly) versus 0.58+/-0.11 (young), p = 0.01] which indicates a more profound cortisol suppression was noted. A significant correlation of -0.61 (p < 0.05) between drug exposure (methylprednisolone AUC) and pharmacologic effect (cortisol suppression ratio) was noted for the combined data in the young and elderly males. During Phase I, the CD4+ and CD8+ lymphocyte AUC was significantly smaller in the elderly. A definite suppression pattern for total, CD4+ and CD8+ lymphocytes and cortisol was noted after methylprednisolone exposure in young and elderly males. An age-dependent suppression of cortisol during Phase II was noted but the degree of lymphopenia after drug exposure did not differ between the young and elderly group for any of the cell subsets. These data from healthy elderly provide a basis for further studies to assess immunologic and endocrinologic responses among elderly patients requiring chronic glucocorticoid therapy.

Protein modification by thermal processing

This paper is a review concerning the way in which heat treatment can modify the allergenicity of food proteins. Any food protein may be allergenic if it can be absorbed intact, or as substantial fragments, through the gut mucosa and then evoke an immune (allergic) response. The intrinsic properties of the protein, the overall composition of the food, and the past processing history (especially thermal processing) all have an effect on the allergic potential. When a protein is denatured by heat, most of the original tertiary structure is lost, so that many of the sites recognized by antibodies on the native molecule are destroyed. There are many examples of allergenicity being reduced, but not eliminated, by heating. But heat-denatured proteins can also present new antigenic sites, uncovered by the unfolding process or created by new chemical reactions with other molecules present in the food (e.g., beta-lactoglobulin associating with alpha-lactalbumin in milk). We have found that heat-denatured beta-lactoglobulin has at least one new epitope, not found in the native state. Therefore, thermal processing can be part of a procedure for making hypoallergenic food, but will rarely be sufficient on its own. Increased understanding will help in evaluating novel proteins and processes.

Drug targeting using low density lipoprotein (LDL): physicochemical factors affecting drug loading into LDL particles

Low density lipoprotein (LDL) has been found suitable as a targeting carrier for cytotoxic drugs. However, higher drug loading into LDL particles without disrupting their native integrity remains a major obstacle. The purpose of this study is to investigate the different physicochemical factors that may affect drug loading and to characterize LDL-drug conjugates. Doxorubicin (Dox) and 3', 5'-O-dipalmitoyl-5-iodo-2'-deoxyuridine (dpIUdR) were used as reference cytotoxic drugs. Drugs were loaded into LDL particles using the dry film method with or without surfactants, liposomal and the direct addition method. The effects of incubation temperature, time and stoichiometry of LDL-drug conjugates on drug loading were investigated. The LDL-drug conjugates were evaluated for their stability and characterized by differential scanning calorimetry (DSC), denatured gel (SDS-PAGE), and electron microscopy (EM). We have suitably incorporated 45+/-10 Dox and 150+/-25 dpIUdR molecules/LDL particle. A seven-fold increase in Dox incorporation was achieved with the liposomal preparation compared to the dry film method. A 4- to 6-h incubation at 37 degreesC was suitable to restore the native structure of LDL particles. No apo B fragmentation of LDL particles was noted on denatured gel. DSC studies showed no change in the Tm of the LDL and the LDL-drug conjugates. An increase in particle size of LDL-dpIUdR, not LDL-Dox was observed in EM compared to the native LDL which may be related to higher incorporation of dpIUdR. The results indicate that physicochemical factors significantly affect drug loading efficiency and may need to be considered to optimize drug incorporation into LDL particles.

Pharmacokinetics of pentoxifylline and its metabolites in healthy mice and in mice infected with Candida albicans

Pentoxifylline has immunomodulatory properties and has been shown to decrease organ damage and improve survival in animals with gram-negative sepsis or endotoxemia. This effect is mediated by a reduction in endotoxin-induced production of tumor necrosis factor alpha (TNF-alpha) by the host. In earlier studies, we observed an unexpected increase in mortality in mice infected with Candida albicans that were given pentoxifylline even though concentrations of TNF-alpha in serum were not affected. The current study was designed to determine whether the pharmacokinetics of pentoxifylline and its metabolites were altered in C. albicans-infected mice and, if so, whether these changes could have contributed to the increased mortality. Noninfected mice and mice infected with C. albicans were treated with pentoxifylline (60 mg/kg of body weight) intraperitoneally every 8 h. Serum was collected from animals after one (day 0), four (day 1), or seven (day 2) injections of pentoxifylline or saline (controls). The first dose was administered 6 h after C. albicans infection. Serum was pooled. Concentrations of pentoxifylline and metabolites I, IV, and V were determined by capillary gas chromatography. Renal function and hepatic profiles were assessed. Pharmacokinetic parameters (maximum concentration of pentoxifylline in serum, half-life, and area under the concentration-time curve from 0 h to infinity [AUC(0)-infinity]) for all noninfected mice were similar and did not differ from those for day 0-infected mice. For day 1-infected mice, values of these three pharmacokinetic parameters for pentoxifylline and metabolite I were increased two- to fourfold over values for noninfected and day 0-infected mice. For metabolites IV and V, the AUC(0)-infinity was increased approximately eightfold over control values. In addition, day 1-infected mice demonstrated evidence of renal and hepatic dysfunction. In summary, C. albicans infection produced marked changes in the pharmacokinetics of pentoxifylline and its metabolites in the mice. The high concentrations of pentoxifylline and its metabolites in serum attained in infected mice may have contributed to the increased mortality of mice with systemic candidiasis.

Induction of Mn SOD in human monocytes without inflammatory cytokine production by a mutant endotoxin

Endotoxin selectively induces monocyte Mn superoxide dismutase (SOD) without affecting levels of Cu,Zn SOD, catalase, or glutathione peroxidase. However, little is known about the structure-activity relationship and the mechanism by which endotoxin induces Mn SOD. In this study we demonstrated that a mutant Escherichia coli endotoxin lacking myristoyl fatty acid at the 3' R-3-hydroxymyristate position of the lipid A moiety retained its full capacity to coagulate Limulus amoebocyte lysate compared with the wild-type E. coli endotoxin and markedly stimulated the activation of human monocyte nuclear factor-kappaB and the induction of Mn SOD mRNA and enzyme activity. However, in contrast to the wild-type endotoxin, it failed to induce significant production of tumor necrosis factor-alpha and macrophage inflammatory protein-1alpha by monocytes and did not induce the phosphorylation and nuclear translocation of mitogen-activated protein kinase. These results suggest that 1) lipid A myristoyl fatty acid, although it is important for the induction of inflammatory cytokine production by human monocytes, is not necessary for the induction of Mn SOD, 2) endotoxin-mediated induction of Mn SOD and inflammatory cytokines are regulated, at least in part, through different signal transduction pathways, and 3) failure of the mutant endotoxin to induce tumor necrosis factor-alpha production is, at least in part, due to its inability to activate mitogen-activated protein kinase.

New directions in perioperative management for pediatric solid organ transplantation

Advances in pediatric solid organ transplantation have furthered the understanding of end-organ failures and refined the strategies for perioperative management of these otherwise lethal diseases. As the donor pool expands, the number of transplantations increases and long-term survival continues to improve, more complete knowledge of the immunologic and pathologic processes will be gained. A thorough understanding of the principles of transplantation medicine remains essential for physicians to provide optimal perioperative care of pediatric organ transplant patients.

Potentiation by thyroid hormone of human IFN-gamma-induced HLA-DR expression

We have investigated the mechanism by which thyroid hormone potentiates IFN-gamma-induced HLA-DR expression. IFN-gamma-induced HLA-DR expression requires activation of STAT1alpha and induction of the Class II trans-activator, CIITA. HeLa and CV-1 cells treated only with L-thyroxine (T4) demonstrated increased tyrosine phosphorylation and nuclear translocation (= activation) of STAT1alpha; this hormone effect on signal transduction, and T4 potentiation of IFN-gamma-induced HLA-DR expression, were blocked by the inhibitors CGP 41251 (PKC) and genistein (tyrosine kinase). Treatment of cells with T4-agarose also caused activation of STAT1alpha. In the presence of IFN-gamma, T4 enhanced cytokine-induced STAT1alpha activation. Potentiation by T4 of IFN-gamma action was associated with increased mRNA for both CIITA and HLA-DR, with peak enhancement at 16 h (CIITA), and 2 d (HLA-DR). T4 increased IFN-gamma-induced HLA-DR protein 2.2-fold and HLA-DR mRNA fourfold after 2 d. Treatment with actinomycin D after induction of HLA-DR mRNA with IFN-gamma, with or without T4, showed that thyroid hormone decreased the t(1/2) of mRNA from 2.4 to 1.1 h. HeLa and CV-1 cells lack functional nuclear thyroid hormone receptor. Tetraiodothyroacetic acid (tetrac) and 3,5,3'-triiodo-thyroacetic acid (triac) blocked T4 potentiation of IFN-gamma-induced HLA-DR expression and T4 activation of STAT1alpha. These studies define an early hormone recognition step at the cell surface that is novel, distinct from nuclear thyroid hormone receptor, and blocked by tetrac and triac. Thus, thyroid hormone potentiation of IFN-gamma-induced HLA-DR transcription is mediated by a cell membrane hormone binding site, enhanced activation of STAT1alpha, and increased CIITA induction.

Long-term efficacy, tolerability, and safety of the combination of enalapril and felodipine ER in the treatment of hypertension. Enalapril-Felodipine ER Factorial Study Group

A recent 8-week, double-masked, placebo-controlled, 3 x 4 factorial-design study demonstrated that enalapril-felodipine extended-release (ER) combinations had statistically significant additive effects for reducing both sitting systolic blood pressure (SiSBP) and sitting diastolic blood pressure (SiDBP) and were generally well tolerated in hypertensive patients with SiDBPs ranging from 95 to 115 mm Hg. The present open-label study was undertaken to assess the long-term efficacy, tolerability, and safety of such combinations. Patients from the factorial study were eligible for the 1-year, open-label extension. Initially, all patients received enalapril 5 mg-felodipine ER 2.5 mg once daily; if SiDBP was not controlled (< 90 mm Hg) after 4 weeks of treatment, the dose was titrated upward at 2- to 4-week intervals to a maximum of enalapril 10 mg-felodipine ER 10 mg. Hydrochlorothiazide (HCTZ) 12.5 mg was added to the regimen of patients whose hypertension was not controlled at the highest enalapril-felodipine ER dose. A total of 507 patients were enrolled, of whom 502 were assessable. At their last study visit, 391 (78%) of the assessable patients were receiving only an enalapril-felodipine ER combination. The enalapril-felodipine ER combinations resulted in mean trough SiDBPs of 85 to 89 mm Hg (decreases of 13 to 16 mm Hg from baseline) and SiSBPs of 137 to 140 mm Hg (decreases of 13 to 21 mm Hg). Overall, 407 (81%) of the 502 assessable patients achieved an SiDBP < 90 mm Hg or a reduction from baseline > or = 10 mm Hg (responders); such a response was recorded in 331 patients (66%) taking a combination of enalapril-felodipine ER alone and 76 patients (15%) taking the combination with the addition of HCTZ 12.5 mg. Blood pressure reductions were maintained throughout the treatment period. Drug-related adverse events were relatively infrequent, often transient, usually mild, and apparently not dose related. The most frequently reported drug-related adverse events were edema/swelling, asthenia/fatigue, dizziness, cough, and headache. These results suggest that combination therapy with enalapril-felodipine ER is effective for long-term blood pressure reduction, has an excellent safety profile, and is generally well tolerated. Addition of low-dose HCTZ to the enalapril-felodipine ER combination appears to provide further blood pressure control without increasing drug-related adverse events.

Identification of epitopes within beta lactoglobulin recognised by polyclonal antibodies using phage display and PEPSCAN

Two different epitope mapping techniques were used to identify linear epitopes recognised by polyclonal IgG antibodies from rabbits immunised with bovine beta lactoglobulin (BLG), which is generally regarded as a major allergen in milk. The first, PEPSCAN, was used to investigate the binding of several rabbit polyclonal antisera to sequential overlapping peptides (12-mers) across the sequence of BLG. Each peptide was synthesized on a different polypropylene PIN, and a standard ELISA procedure was used to locate which of these peptides bound the antibodies under investigation. Comparisons of PEPSCANs for antisera from six different rabbits showed that each rabbit recognized a similar set of epitopes within BLG. PEPSCAN analysis also showed that polyclonal antibodies from the mouse recognize a set of epitopes similar to those recognized by the rabbit. The second epitope mapping technique is known as phage display and utilizes libraries of randomized short peptides fused to the coat proteins of filamentous phage as a source of epitopes for analysis. A gene VIII phage display library was used in this study with constrained nonapeptides, which were screened for epitopes recognized by affinity purified rabbit anti-BLG IgG. Immobilised rabbit anti-BLG IgG was screened in two separate experiments, each consisting of three rounds of panning. For each separate experiment, a sensitive phage ELISA was used to screen several hundred single phage clones for binding to anti-BLG IgG immobilised on microtiter plates. As a result, a number of positive phage were identified from the two separate screens of the library (19 different peptides were isolated, which resembled four different regions of BLG). The identified sequences were found to constitute a subset of the linear epitopes recognized by the PEPSCAN technique. The coordinates of the crystal structure of BLG were used to display mapped epitopes on its structure. This study has permitted detailed mapping of the major linear antigenic regions within BLG recognised by IgG antibodies from immunised rabbits and mice.

The effects of pentoxifylline infusion on plasma 6-keto-prostaglandin F1 alpha and ex vivo endotoxin-induced tumour necrosis factor activity in horses

Pentoxifylline (7.5 mg/kg) was bolused intravenously to eight healthy horses and was immediately followed by infusion (1.5 mg/kg/h) for 3 h. Clinical parameters were recorded and blood samples were collected for 24 h. Plasma was separated and concentrations of pentoxifylline, its reduced metabolite I, and 6-keto-prostaglandin F1 alpha were determined. Heparinized whole blood was also incubated ex vivo with 1 ng Escherichi coli endotoxin/mL blood for 6 h before determination of plasma tumour necrosis factor activity. The peak plasma concentrations of pentoxifylline and metabolite I occurred at 15 min after bolus injection and were 9.2 +/- 1.4 and 7.8 +/- 4.3 micrograms/mL, respectively. The half-life of elimination (t1/2 beta) of pentoxifylline was 1.44 h and volume of distribution (Vdarea) was 0.94 L/kg. The mean plasma concentration of 6-keto-prostaglandin F1 alpha increased over time, with a significant increase occurring 30 min after the bolus administration. Ex vivo plasma endotoxin-induced tumour necrosis factor activity was significantly decreased at 1.5 and 3 h of infusion. These results indicate that infusion of pentoxifylline will increase 6-keto-prostaglandin F1 alpha and significantly suppress endotoxin-induced tumour necrosis factor activity in horses during the period of infusion.

Protein synthesis-dependent potentiation by thyroxine of antiviral activity of interferon-gamma

We have studied the prenuclear signal transduction pathway by which thyroid hormone potentiates the antiviral activity of human interferon-gamma (IFN-gamma) in HeLa cells, which are deficient in thyroid hormone receptor (TR). The action of thyroid hormone was compared with that of milrinone, which has structural homologies with thyroid hormone. L-Thyroxine (T4), 3,5,3'-L-triiodothyronine (T3), and milrinone enhanced the antiviral activity of IFN-gamma up to 100-fold, a potentiation blocked by cycloheximide. The 5'-deiodinase inhibitor 6-n-propyl-2-thiouracil did not block the T4 effect. 3,3',5,5'-Tetraiodothyroacetic acid prevented the effect of T4 but not of milrinone. The effects of T4 and milrinone were blocked by inhibitors of protein kinases C (PKC) and A (PKA) and restored by PKC and PKA agonists; only the effect of T4 was blocked by genistein, a tyrosine kinase inhibitor. In separate models, milrinone was shown not to interact with nuclear TR-beta. T4 potentiation of the antiviral activity of IFN-gamma requires PKC, PKA, and tyrosine kinase activities but not traditional TR.

Single-dose ondansetron prevents postoperative vomiting in pediatric outpatients

This randomized, double-blind, parallel-group, multicenter study evaluated the safety and efficacy of ondansetron (0.1 mg/kg to 4 mg intravenously) compared with placebo in the prevention of postoperative vomiting in 429 ASA status I-III children 1-12 yr old undergoing outpatient surgery under nitrous oxide- and halothane-based general anesthesia. The results show that during both the 2-h and the 24-h evaluation periods after discontinuation of nitrous oxide, a significantly greater percentage of ondansetron-treated patients (2 h 89%, 24 h 68%) compared with placebo-treated patients (2 h 71%, 24 h 40%) experienced complete response (i.e., no emetic episodes, not rescued, and not withdrawn; P < 0.001 at both time points). Ondansetron-treated patients reached criteria for home readiness one-half hour sooner than placebo-treated patients (P < 0.05). The age of the child, use of intraoperative opioids, type of surgery, and requirement to tolerate fluids before discharge may also have affected the incidence of postoperative emesis during the 0- to 24-h observation period. Use of postoperative opioids did not have any effect on complete response rates in this patient population. We conclude that the prophylactic use of ondansetron reduces postoperative emesis in pediatric patients, regardless of the operant influential factors.

IMPLICATIONS

Postoperative nausea and vomiting often occur after surgery and general anesthesia in children and are the major reason for unexpected hospital admission after ambulatory surgery. Our study demonstrates that the prophylactic use of a small dose of ondansetron reduces postoperative vomiting in pediatric patients.

Cholesterol in condensed and fluid phosphatidylcholine monolayers studied by epifluorescence microscopy

Epifluorescence microscopy was used to investigate the effect of cholesterol on monolayers of dipalmitoylphosphatidylcholine (DPPC) and 1 -palmitoyl-2-oleoyl phosphatidylcholine (POPC) at 21 +/- 2 degrees C using 1 mol% 1-palmitoyl-2-[12-[(7-nitro-2-1, 3-benzoxadizole-4-yl)amino]dodecanoyl]phosphatidylcholine (NBD-PC) as a fluorophore. Up to 30 mol% cholesterol in DPPC monolayers decreased the amounts of probe-excluded liquid-condensed (LC) phase at all surface pressures (pi), but did not effect the monolayers of POPC, which remained in the liquid-expanded (LE) phase at all pi. At low pi (2-5 mN/m), 10 mol% or more cholesterol in DPPC induced a lateral phase separation into dark probe-excluded and light probe-rich regions. In POPC monolayers, phase separation was observed at low pi when > or =40 mol% or more cholesterol was present. The lateral phase separation observed with increased cholesterol concentrations in these lipid monolayers may be a result of the segregation of cholesterol-rich domains in ordered fluid phases that preferentially exclude the fluorescent probe. With increasing pi, monolayers could be transformed from a heterogeneous dark and light appearance into a homogeneous fluorescent phase, in a manner that was dependent on pi and cholesterol content. The packing density of the acyl chains may be a determinant in the interaction of cholesterol with phosphatidylcholine (PC), because the transformations in monolayer surface texture were observed in phospholipid (PL)/sterol mixtures having similar molecular areas. At high pi (41 mN/m), elongated crystal-like structures were observed in monolayers containing 80-100 mol% cholesterol, and these structures grew in size when the monolayers were compressed after collapse. This observation could be associated with the segregation and crystallization of cholesterol after monolayer collapse.

Microbial models of mammalian metabolism. Biotransformations of HP 749 (besipirdine) using Cunninghamella elegans

HP 749 (besipirdine; Hoechst-Roussel Pharmaceuticals, Inc., Somerville, NJ) and related analogs belonging to the N-(4-pyridinyl)-1H-indol-1-amine class of compounds have shown a potential to mitigate multiple biochemical deficits associated with Alzheimer's disease. HP 749 has demonstrated cholinergic and nonadrenergic activities both in vitro and in vivo, and has potential for the symptomatic treatment of Alzheimer's disease. The three primary metabolites of HP 749 in dogs, rats, and humans result from hydroxylation of the indole ring, N-dealkylation of the parent compound, and sequential hydroxylation and dealkylation. The fungus Cunninghamella elegans (ATCC 36112) converts 25% of HP 749 in a dextrose broth to yield four metabolites, three of which have been reported in mammalian systems. Preparative scale fermentation allowed for the isolation of the major fungal metabolite resulting from hydroxylation of the indole nucleus at position 5 (16%), which was characterized by cochromatographic (TLC and HPLC), 1H-NMR, mass spectral (chemical ionization/MS), and UV comparisons to a synthetic standard. Additional minor fungal metabolites were formed as a result of N-dealkylation (2%), and sequential N-dealkylation and aromatic hydroxylation (2.5%). C. elegans is being used as a model to help predict and generate the logical mammalian metabolites of related structural analogs of HP 749.

A randomized multicenter study of remifentanil compared with alfentanil, isoflurane, or propofol in anesthetized pediatric patients undergoing elective strabismus surgery

Remifentanil hydrochloride is a new, ultrashort-acting opioid metabolized by nonspecific plasma and tissue esterases. We conducted this multicenter study to examine the hemodynamic response and recovery profile of premedicated children undergoing strabismus repair who were randomly assigned to receive one of four treatment drugs (remifentanil, alfentanil, isoflurane, or propofol) along with nitrous oxide and oxygen for maintenance of anesthesia. Induction of anesthesia was by nitrous oxide, oxygen, and halothane or nitrous oxide, oxygen, and propofol. Anesthesia was then maintained with remifentanil 1.0 microgram/kg over 30-60 s, followed by a constant infusion of 1.0 microgram.kg-1.min-1, alfentanil 100 micrograms/kg bolus followed by a constant infusion of 2.5 micrograms.kg-1.min-1, propofol 2.5 mg/kg bolus followed by a constant infusion of 200 micrograms.kg-1.min-1, or isoflurane 1.0 minimum alveolar anesthetic concentration. The infusions of the anesthetics and the administration of the inhaled gases were adjusted clinically by predetermined protocols. Elapsed time intervals from the end of surgery to the time the patients were tracheally extubated and displayed purposeful movement, as well as the time the patients met the postanesthesia care unit (PACU) and hospital discharge times, were recorded. Heart rate and systolic and diastolic blood pressure were measured at fixed intervals. In addition, cardiovascular side effects (bradycardia, hypotension, and hypertension) as well as vomiting, pruritus, agitation, and postoperative hypoxemia were also noted. There were no significant differences in patient demographics among the treatment groups. There was no difference in the early recovery variables (times to extubation and purposeful movement) or the times to PACU and hospital discharge among groups. There were significant differences in side effects among the groups. Patients who received remifentanil had higher PACU objective pain-discomfort scores than those who received alfentanil and propofol. Patients anesthetized with alfentanil had a greater incidence in the use of naloxone and a greater incidence of postoperative hypoxemia compared with those anesthetized with remifentanil. The incidence of postoperative hypoxemia was the same for remifentanil, propofol, and isoflurane groups. There were no significant differences in the incidence of emesis among the four groups, and all four groups had similar hemodynamic profiles. We conclude that remifentanil appears to be an effective drug for anesthesia. Its hemodynamic and recovery profile appear similar to other comparable drugs. Based on previous pharmacokinetic studies, the 1.0 microgram.kg-1.min-1 infusion may be twice the 50% effective dose observed in adults. In this study, the relative "overdose" of remifentanil was well tolerated and did not prolong recovery.

Time course and involvement of protein kinase C-mediated phosphorylation of F1/GAP-43 in area CA3 after mossy fiber stimulation

1. Protein kinase C (PKC) activity and phosphorylation of F1/growth associated protein (GAP)-43, a PKC substrate, have been proposed to play key roles in the maintenance of long-term potentiation (LTP) at the synapses of Schaffer collateral/commissural on pyramidal neurons in CA1 (Akers et al., 1986). We have studied in the involvement of PKC and PKC-dependent protein phosphorylation of F1/GAP-3 in in vitro LTP observed at the synapses of mossy fiber (MF) on CA3 pyramidal neurons of rat hippocampus by post hoc in vitro phosphorylation. 2. After LTP was induced in CA3 in either the presence or absence of D-2-amino-5-phosphonovaleric acid (AP5), an NMDA receptor antagonist, the CA3 region was dissected for in vitro phosphorylation assay. In vivo phosphorylation of F1/GAP-43 was increased in membranes at 1 and 5 min after tetanic stimulation (TS) but not at 60 min after TS. 3. The degree of phosphorylation of F1/GAP-43 in the cytosol was inversely related to that in membranes at each time point after LTP. 4. The similar biochemical changes obtained from either control slices or AP5-treated slices indicate that LTP and the underlying biochemical changes are independent of the NMDA receptor. Immunoreactivity of the phosphorylated F1/GAP-43 in LTP slices was not significantly different from control, indicating that results from western blotting and post hoc in vitro phosphorylation are consistent. 5. Post hoc in vitro phosphorylation of F1/GAP-43 was PKC-mediated since phosphorylation of F1/GAP-43 was altered by the PKC activation cofactors, Ca2+, phosphatidylserine and phorbol ester. 6. Calmodulin (CaM) at > 5 microM inhibited phosphorylation, consistent with the presence of CaM-binding activity at the site on F1/GAP-43 acted upon by PKC. 7. We conclude that phosphorylation of F1/GAP-43 is associated with the induction but not the maintenance phase of MF-CA3 LTP.

Structure of a glycoconjugate in solution and in complex with an antibody Fv fragment

By use of heteronuclear (13C, 1H) NMR methods, the three-dimensional structure and dynamics of the glycoconjugate estrone-3-glucuronide (E3G) uniformly 13C enriched in the glucuronic acid moiety has been probed both in free solution and in association with an anti-E3G antibody single-chain Fv fragment. The glycan is found to exist in multiple conformations in free solution, with particularly large torsional fluctuations about the glycosidic linkage psi. Resonance assignments and distance restraints for the glycoconjugate in the bound state were obtained from heteronuclear proton-carbon-carbon-proton-COSY and isotope-edited NOESY techniques, respectively. Quantitation of the NOE data with a full-relaxation matrix approach showed that the antibody selects a conformation from the solution repertoire which does not correspond with either of the two lowest energy conformations of the free glycan, and the internal energy of the glycan in the bound state is estimated to be at most approximately 15 kcal/mol higher than the global minimum energy conformation. The glucuronide moiety undergoes a stacking interaction with an aromatic ring in the binding site, and both ring-current shifts and nuclear Overhauser effects computed from the predicted bound-state conformation are in good agreement with experiment. The bound-state conformation is also in good agreement with preliminary x-ray data on a related complex.

Cortisol pharmacodynamics after methylprednisolone administration in young and elderly males

Glucocorticoids are commonly prescribed in the elderly on an empiric basis with little consideration for the age-related alterations in pharmacologic response. The objectives of this study were to compare the effect of methylprednisolone on cortisol patterns in elderly and young healthy men, to define the relationship between pharmacokinetic parameters of methylprednisolone and pharmacodynamics of cortisol in the elderly and young men. Seven healthy, elderly males (69-82 years old) and five healthy, young males (24-37 years old) participated in a 24-hour pharmacodynamic trial with randomized assignment to a control period (Phase 1) and a methylprednisolone period (Phase II). Serial blood samples were obtained throughout both study periods. Cortisol measurements included the total area under the concentration-time curve (AUC), return AUC, and suppression ratio. During Phase I, a circadian pattern was noted in both groups. After exposure to methylprednisolone (Phase II), a linear decline in serum concentrations of cortisol was observed in both groups. The return AUC of cortisol (425 +/- 357 ng.hr/mL [elderly] versus 854 +/- 216 ng.mL [young]) and the total AUC 764 +/- 340 ng.h/mL [elderly] versus 1,230 +/- 258 ng.hr/mL [young]) were significantly lower in the older men. In addition, a significant decline in total AUC and nadir concentration of cortisol from Phase I to Phase II was noted within both groups. The suppression ratio was significantly greater in the elderly men (mean, 0.38 versus 0.58 in young), which indicates a greater degree of adrenal suppression after administration of methylprednisolone. Exposure to methylprednisolone, as measured by AUC, was 554 +/- 215 ng.hr/kg (elderly) and 389 +/- 102 ng.hr/kg (young). The greater exposure to methylprednisolone noted in the elderly yielded significant combined correlations for both groups with AUC, return AUC, and suppression ratio of cortisol. A more significant response of cortisol to the exogenous glucocorticoid was apparent in the elderly men. In addition, a slower clearance of methylprednisolone was noted in the elderly group compared with their young counterparts. The effect of reduced clearance of methylprednisolone on the suppression ratio indicates the interrelationship between the disposition of a single dose of an exogenous glucocorticoid and response patterns of cortisol.

Combined enalapril and felodipine extended release (ER) for systemic hypertension. Enalapril-Felodipine ER Factorial Study Group

This multicenter, placebo-controlled, double-blind trial of factorial design evaluated the safety and efficacy of combination treatment with the angiotensin-converting enzyme inhibitor, enalapril, and the vascular selective calcium antagonist felodipine extended release (ER) in patients with essential hypertension. After a 4-week, single-blind placebo baseline period, 707 patients with sitting diastolic blood pressures (BPs) in the range of 95 to 115 mm Hg received placebo, enalapril (5 or 20 mg), felodipine ER (2.5, 5, or 10 mg), or their combinations for an 8-week double-blind treatment period. All doses of enalapril and felodipine ER had a statistically significant (p < 0.05) additive effect in reducing both systolic and diastolic BP. The trough to peak ratios for the combinations ranged from 0.63 (enalapril 5 mg-felodipine ER 2.5 mg) to 0.79 (enalapril 20 mg-felodipine ER 10 mg) and were consistent with effective BP control with 1 dose/day. Patients aged > or = 65 years demonstrated a greater reduction in diastolic BP. Combinations of enalapril-felodipine ER were associated with less drug-induced peripheral edema (4.1%) compared to felodipine ER monotherapy (10.8%). There were no serious drug-related adverse effects observed during the study. In this trial, the combination of enalapril and felodipine ER effectively lowered BP and was generally well tolerated with an excellent safety profile when used in the treatment of hypertension.

Fentanyl and alfentanil plasma protein binding in preterm and term neonates

The effects of gestational age (GA) and plasma protein concentrations on the plasma protein binding of fentanyl and alfentanil were studied in preterm and term neonates. Binding experiments were performed using split-cell equilibrium dialysis. Fentanyl and alfentanil concentrations were measured using specific radioimmunoassay, and the proteins albumin and alpha-1-acid glycoprotein (AAG) were measured using radial immunodiffusion assays. In the preterm neonates, 77% of fentanyl and 65% of alfentanil was bound. In the term neonates, 70% of fentanyl and 79% of alfentanil was bound. The binding ratio of alfentanil showed a positive correlation with gestational age and AAG concentration. The binding ratio of fentanyl showed a weak, negative correlation with gestational age. These data indicate that fentanyl and alfentanil are not interchangeable at the GA studied because of age-related changes in protein binding.

Speech breathing and the Lombard effect

Respiratory measurements were made using linearized magnetometers placed antero-posteriorly over the rib cages and abdomens of five healthy young women. Background noise was introduced over headphones simultaneously as "babble" presented binaurally at 55 dB ("moderate noise") and 70 dB ("high noise"). Speech during oral reading and spontaneous monologue was transduced with a microphone positioned near the lips, from which a speaking intensity signal (dBA) was derived. Subjects were instructed to speak during the noise conditions, but no instruction was given to alter speaking intensity. Compared with a "no noise" condition, the speaking intensities of all the subjects increased significantly for both speech tasks in the moderate and high noise conditions, thereby replicating the well-documented Lombard effect. No consistent trend of lung volume change was observed, in contrast to the linear increases in speech intensity as the noise level increased. For the higher speech intensities during the moderate and high noise conditions both initiation and termination lung volumes either increased or decreased. These preliminary findings suggest that when speech intensity is increased following the introduction of noise via headphones rather than by specific instruction to speak more loudly, speakers employ variable lung volume strategies for intensity control.

Thermal history alters cholesterol effect on transition of 1-palmitoyl-2-linoleoyl phosphatidylcholine

The effect of cholesterol on the bilayer phase behavior of heteroacid phosphatidylcholines with one unsaturated fatty acid depends on the nature of the unsaturated chain. Previous differential scanning calorimetry (DSC) studies showed that 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (16:0-18:2 PC) had a broad, weak transition at about -18 degrees C, which was effectively eliminated by less than 15 mol% cholesterol. Phospholipids with greater and lesser degrees of unsaturation displayed stronger phase transitions and less sensitivity to cholesterol. In this work, deuterium nuclear magnetic resonance has been used to examine the phase behavior of 1-perdeuteriopalmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (16:0-18:2 PC-d31) alone, and with 15 mol % cholesterol. The behavior is found to be sensitive to sample thermal history. Moderately fast cooling (1 degree/h) results in a continuous phase change from a fluid to an ordered phase in the pure lipid. Under similar cooling conditions, the sample containing cholesterol displays increased chain order and a continuous phase change with no apparent isothermal transition. However, when these systems are cooled at a reduced rate (0.3 degree/h), the continuous phase change is pre-empted by a sharp transition into a more ordered phase that gives a deuterium spectrum having intensity at a value of the quadrupole-splitting characteristic of a rigid lattice system. In the pure lipid, this transition effectively coincides with the center of the continuous phase change. Addition of 15 mol % cholesterol lowers the temperature of this sharp transition by about 3 degrees C. These observations provide some insights into the behavior of this system seen using differential scanning calorimetry. Results of deuteron transverse relaxation measurements under these conditions are also reported.