Trivalent inactivated influenza vaccine safety in children: Assessing the contribution of telephone encounters

We assessed the contribution of telephone medical care encounters to surveillance of adverse events (AE) following trivalent influenza vaccination in children age 6 months to 17 years. We used retrospective, self-controlled, case-series analysis to estimate adverse event incidence rate ratios for post-vaccination risk intervals relative to 15-28 days prior to vaccination. We confirmed possible vaccination reactions by medical record abstraction. Detection of 10 of 20 elevated incidence rate ratios required telephone data. We conclude that telephone encounters substantially contribute to the detection of possible influenza vaccination reactions, primarily local injection site and systemic reactions.

Characterization of key residues in the subdomain encoded by exons 8 and 9 of human inducible nitric oxide synthase: a critical role for Asp-280 in substrate binding and subunit interactions

Human inducible nitric oxide synthase (iNOS) is active as a dimer of two identical subunits. Each subunit has an amino-terminal oxygenase domain that binds the substrate l-Arg and the cofactors heme and tetrahydrobiopterin and a carboxyl-terminal reductase domain that binds FMN, FAD, and NADPH. We previously demonstrated that a subdomain in the oxygenase domain encoded by exons 8 and 9 is important for dimer formation and NO synthesis. Further, we identified Trp-260, Asn-261, Tyr-267, and Asp-280 as key residues in that subdomain. In this study, using an Escherichia coli expression system, we produced, purified, and characterized wild-type iNOS and iNOS-Ala mutants. Using H(2)O(2)-supported oxidation of N(omega)-hydroxy-l-Arg, we demonstrate that the iNOS mutants' inabilities to synthesize NO are due to selective defects in the oxygenase domain activity. Detailed characterization of the Asp-280-Ala mutant revealed that it retains a functional reductase domain, as measured by its ability to reduce cytochrome c. Gel permeation chromatography confirmed that the Asp-280-Ala mutant exists as a dimer, but, in contrast to wild-type iNOS, urea-generated monomers of the mutant fail to reassociate into dimers when incubated with l-Arg and tetrahydrobiopterin, suggesting inadequate subunit interaction. Spectral analysis reveals that the Asp-280-Ala mutant does not bind l-Arg. This indicates that, in addition to dimerization, proper subunit interaction is required for substrate binding. These data, by defining a critical role for Asp-280 in substrate binding and subunit interactions, give insights into the mechanisms of regulation of iNOS activity.

Lumbosacral cerebrospinal fluid volume is the primary determinant of sensory block extent and duration during spinal anesthesia

BACKGROUND. Injection of local anesthetic into cerebrospinal fluid (CSF) produces anesthesia of unpredictable extent and duration. Although many factors have been identified that affect the extent of spinal anesthesia, correlations are relatively poor and the extent of spread remains unpredictable. This study was designed to determine whether variability in the volume of lumbosacral CSF among individuals is a contributing factor in the variability of spinal anesthesia.

METHODS

Spinal anesthesia was administered to 10 healthy volunteers with 50 mg lidocaine in 7.5% dextrose. The technique was standardized to minimize variability in factors known to affect the distribution of spinal anesthesia. The extent of sensory anesthesia was assessed by pin-prick and by transcutaneous electrical stimulation. Motor blockade was assessed in the quadriceps and gastrocnemius muscles by force dynamometry. Duration of anesthesia was assessed by pinprick, transcutaneous electrical stimulation, and duration of motor blockade. Lumbosacral CSF volumes were calculated from low thoracic, lumbar, and sacral axial magnetic resonance images obtained at 8-mm increments. Volumes of CSF were correlated with measures of extent and duration of spinal anesthesia using the Kendall rank correlation test.

RESULTS

Lumbosacral CSF volumes ranged from 42.7 to 81.1 ml. Volumes of CSF correlated with pin-prick assessments of peak sensory block height (P = 0.02) and duration of surgical anesthesia (as assessed by the duration of tolerance to transcutaneous electrical stimulation at the ankle (P < 0.05).

CONCLUSIONS

Variability in lumbosacral CSF volume is the most important factor identified to date that contributes to the variability in the spread of spinal sensory anesthesia.

An explanation and the clinical significance of the failure of microcolumn tests to detect weak ABO and other antibodies

Shear forces are proposed to explain the failure of antiglobulin and 'neutral' (no antiglobulin) microcolumn tests at 37 degrees C to detect weak ABO incompatibilities and other weak antibodies, clearly detectable by spin-tube methods. These shear forces can be minimized in a microcolumn test using a biphasic centrifugation phase. Although this biphasic test is not suitable for routine use, it may be of use as an investigational method for reference laboratories. This failure of microcolumn test to detect weak ABO incompatibilities is of little clinical significance as the antibodies are dubiously active at 37 degrees C.

Autologous mixed lymphocyte reaction in patients with myasthenia gravis: correlation with disease activity

Enriched subpopulations of peripheral blood mononuclear cells from patients with myasthenia gravis and from normal control individuals were tested for proliferative ability in the autologous mixed lymphocyte reactions. Myasthenia gravis patients were studied at various phases of therapy. Longitudinal patient populations were studied. Purified T cells from untreated patients with active myasthenia gravis demonstrated enhanced proliferative responses when co-cultured with nonmodified autologous non-T cells. Furthermore, treatment by thymectomy with or without prior plasmapheresis was associated with a consequent normalization of the autologous reaction. The enhanced autologous mixed lymphocyte reaction in the pre-treatment group of myasthenia gravis patients was significantly different from the post-treatment and normal control groups (Stimulation Index, p less than 0.01 and p less than 0.02, respectively). This difference in activity was also confirmed in a longitudinal study of 10 patients followed pre- and post-treatment (Stimulation Index, p less than 0.02). There was no difference between the responses of post-treatment patients and normal control individuals. There was no evidence of altered T cell responsiveness or non-T cell stimulation, as measured by the allogeneic mixed lymphocyte reaction or by mitogen-induced lymphocyte proliferation, between pretreatment and post-treatment patients as compared to controls. The responses were not affected by serum substitution experiments whereby myasthenic responder T cells were co-cultured with pooled normal human sera. Other parameters studied included clinical status, anti-acetylcholine receptor antibody levels, and thymic pathology. An intriguing connection between abnormalities in the thymic cell populations and the autoaggressive state in myasthenia may be reflected by the in vitro autologous mixed lymphocyte reaction.

Autologous mixed lymphocyte reaction in patients with myasthenia gravis: correlation with disease activity

Enriched subpopulations of peripheral blood mononuclear cells from patients with myasthenia gravis and from normal control individuals were tested for proliferative ability in the autologous mixed lymphocyte reactions. Myasthenia gravis patients were studied at various phases of therapy. Longitudinal patient populations were studied. Purified T cells from untreated patients with active myasthenia gravis demonstrated enhanced proliferative responses when co-cultured with nonmodified autologous non-T cells. Furthermore, treatment by thymectomy with or without prior plasmapheresis was associated with a consequent normalization of the autologous reaction. The enhanced autologous mixed lymphocyte reaction in the pre-treatment group of myasthenia gravis patients was significantly different from the post-treatment and normal control groups (Stimulation Index, p less than 0.01 and p less than 0.02, respectively). This difference in activity was also confirmed in a longitudinal study of 10 patients followed pre- and post-treatment (Stimulation Index, p less than 0.02). There was no difference between the responses of post-treatment patients and normal control individuals. There was no evidence of altered T cell responsiveness or non-T cell stimulation, as measured by the allogeneic mixed lymphocyte reaction or by mitogen-induced lymphocyte proliferation, between pretreatment and post-treatment patients as compared to controls. The responses were not affected by serum substitution experiments whereby myasthenic responder T cells were co-cultured with pooled normal human sera. Other parameters studied included clinical status, anti-acetylcholine receptor antibody levels, and thymic pathology. An intriguing connection between abnormalities in the thymic cell populations and the autoaggressive state in myasthenia may be reflected by the in vitro autologous mixed lymphocyte reaction.

Modified semiautomated method for free fatty acids in serum

Modifications have been made to the reagent system of the semiautomated method for the determination of plasma free fatty acids by Baird et al. (1967), and results are reported of investigations into parameters affecting sensitivity and analytical range.