Effects of glucose, Trolox-C, and glutathione disulphide on lipid peroxidation and cell death induced by oxidant stress in rat heart

OBJECTIVE

The aim was to find effective protection of myocytes against peroxide induced damage in terms of preservation of contractile activity, protection against lipid peroxidation, and protection against cell death.

METHODS

The components of the glutathione redox cycle, the production of malondialdehyde, cell contractions, and enzyme release from myocytes were measured in cultured neonatal rat heart cells before and after administration of cumene hydroperoxide, 80 mumol.litre-1. The protective action was tested of (1) glucose (10 mmol.litre-1) which stimulates the production of NADPH; (2) Trolox-C (0.16 mmol.litre-1) which is a water soluble analogue of alpha tocopherol and a scavenger of free radicals; and (3) GSSG (0.6 mmol.litre-1) which increases the intracellular concentrations of GSH and GSSG.

RESULTS

Although the three substances tested were equally effective in reducing the formation of malondialdehyde, exogenous GSSG afforded only slight protection against cumene hydroperoxide induced cell death, whereas glucose and Trolox-C were highly effective protectors. The depressant effect of cumene hydroperoxide on beating frequency was not influenced by preincubation with GSSG, nor by coadministration of glucose, but Trolox-C was able to diminish the negative chronotropic action of cumene hydroperoxide.

CONCLUSIONS

Effective protection against cumene hydroperoxide induced lipid peroxidation is not associated per se with effective protection against cumene hydroperoxide induced loss of beating frequency and cell death.

Relative value of diagnostic tests for small acoustic neuromas

Auditory brainstem response is now widely employed as a screening test for acoustic neuromas because it is equally sensitive when standardized against computed tomography. We have detected eight small (less than 10 mm) acoustic neuromas using gadolinium enhanced magnetic resonance imaging. In three of these cases, the auditory brainstem response was falsely negative. In contrast, 19 patients with larger tumors (greater than or equal to 10 mm) were found to have no false negative auditory brainstem responses. Auditory brainstem response appears to be less sensitive for detecting small, symptomatic acoustic neuromas.

Homogeneity of the relative risk in cohort studies

We propose a statistical method to test the homogeneity of relative risk in cohort studies. We illustrate its application to an original data set from a low-risk group of end-stage renal disease patients on haemodialysis. The use of the method is as a global test against the omnibus alternative.

Resolution of otitis media with effusion with the use of a stepped treatment regimen of trimethoprim-sulfamethoxazole and prednisone

This double blind, placebo-controlled trial was designed to determine whether intervention with a stepped regimen of trimethoprim-sulfamethoxazole (TMP-SMX) and prednisone would prevent high risk children from developing chronic otitis media with effusion (OME) and recurrent acute otitis media. Forty-two children were enrolled, assigned to treatment with active drug or placebo and then examined at 2-week intervals. They received TMP-SMX (or placebo) during the first 2 weeks, TMP-SMX and prednisone (or placebo) during Weeks 3 and 4 for persistent OME and TMP-SMX (or placebo) for Weeks 5 and 6 if OME was still unresolved. After treatment 48% of active drug and 14% of placebo subjects resolved OME bilaterally (P less than 0.05). Active drug subjects also had fewer acute otitis media episodes than placebo subjects while receiving study treatment (P less than 0.01). Although this treatment regimen produced short term OME resolution, long term benefits were not demonstrated.

Tests of homogeneity for the relative risk in multiply-matched case-control studies

We examine several tests of homogeneity of the odds ratio in the analysis of 2 x 2 tables arising from epidemiologic 1:R matched case-control studies. The T4 and T5 statistics proposed by Liang and Self (1985, Biometrika 72, 353-358) are unable to detect obvious inhomogeneity in two numerical examples and in simulation studies. The null hypothesis is rejected by the chi-square statistic of Ejigou and McHugh (1984, Biometrika 71, 408-411) and by a new proposed method whose significance level must be simulated.

Cellular changes in Reissner's membrane in endolymphatic hydrops

A quantitative morphologic study of the cellular changes in human Reissner's membrane (RM) was performed under light microscopy on 30 normal temporal bones from 15 subjects, and on 20 temporal bones from 10 subjects with endolymphatic hydrops. The cellular density of the epithelial and mesothelial layers of normal RMs decreased with increasing age. In endolymphatic hydrops, cellular proliferation and decreased cellular density of a distended RM were observed, and these changes occurred more remarkably in epithelial cells. Decreased cellular density in RM was correlated to the degree of endolymphatic hydrops. These findings indicate an involvement of the epithelial cellular changes in the pathogenesis of endolymphatic hydrops. Our results suggest that cellular changes in RM may cause dysfunction of radial flow leading to ionic disturbance of endolymph, which provides a possible mechanism of hearing loss in endolymphatic hydrops.

An experimental model for measuring middle ear antimicrobial drug penetration in otitis media

Bacteria are an important cause of acute otitis media and successful treatment depends on achieving inhibitory or bacteriacidal antimicrobial drug concentrations in the middle ear. To evaluate further otitis media treatment success and failure, we developed a chinchilla model to study antimicrobial drug penetration through the middle ear mucosa. Using quantitative histomorphometry, we measured the middle ear space in 10 chinchillas and found a mean +/- SD volume of 2.09 +/- 0.08 ml and a mean +/- SD surface area of 14.41 +/- 1.48 cm2. To measure the apparent rate constant (Kc) of antibiotic elimination from the middle ear, through the middle ear mucosa, an antibiotic solution was inoculated into the middle ear cavity, and samples were aspirated between 1 and 8 hr later. In normal ears, the mean Kc +/- SD for amoxicillin was 0.118 +/- 0.013 hr-1, that for a trimethoprim 0.461 +/- 0.090 hr-1, and that for sulfamethoxazole 0.265 +/- 0.062 hr-1. In ears inoculated with type 7F Streptococcus pneumoniae to induce acute otitis media, the Kc +/- SD increased for all three drugs (P less than 0.05): amoxicilin to 0.286 +/- 0.089 hr-1, trimethoprim to 0.662 +/- 0.118 hr-1, and sulfamethoxazole to 0.411 +/- 0.056 hr-1. These values demonstrate that amoxicillin had the lowest apparent penetration rate constant of the three antibiotics but the greatest increase from normal to infected mucosa (142%). Trimethoprim had the highest apparent penetration rate constant of the three antibiotics but the smallest increase from normal to infected mucosa (44%), while the sulfamethoxazone apparent penetration rate constant increased from normal to infected mucosa by 55%.(ABSTRACT TRUNCATED AT 250 WORDS)

Statistical methods for determining risk factors of chronic otitis media with effusion

We use logistic regression with paired Bernouilli outcomes to analyse data on subjects who have either one or two organs (e.g. ears) each of which may develop disease. In this model, subject-specific covariates are related to the probability of developing disease. The proposed method is applied to determine risk factors for chronic otitis media with effusion.

Experimental animal models for studying antimicrobial pharmacokinetics in otitis media

Antimicrobial treatment of otitis media, especially drug dosing considerations, is largely empiric, with few reported pharmacologic studies of drug distribution into the middle ear. A chinchilla animal model of serous and purulent otitis media has been used for some time to investigate mechanisms of disease pathogenesis. This model was adapted to investigate the penetration of amoxicillin, trimethoprim, and sulfamethoxazole into middle ear effusion. Purulent otitis media was produced by direct middle ear inoculation with type 7F Streptococcus pneumoniae. Serous otitis media was produced by eustachian tube obstruction using silastic sponge or Coeflex cement, but the Coeflex caused an undesirable local inflammatory response. The three antibiotics were administered to chinchillas with serous and purulent middle ear effusion. Plasma and ear fluid drug concentrations were measured by liquid chromatography and demonstrated the value of this model in assessing antibiotic penetration.

Bronchodilation from intravenous theophylline in patients with cystic fibrosis: results of a blinded placebo-controlled crossover clinical trial

Most patients with cystic fibrosis (CF) eventually develop chronic obstructive pulmonary disease and theoretically could benefit from theophylline therapy. The purpose of this study was to investigate the pharmacologic response to intravenous theophylline by pulmonary function tests (PFT) and the theophylline pharmacokinetics in patients with CF. A randomized, double-blind, placebo-controlled, crossover trial was conducted in 10 ambulant patients with CF (5 females, 5 males), aged 11 to 21 years. Each patient received an intravenous dose of theophylline and normal saline over 1/2 hour on consecutive days. Spirometry and whole-body plethysmography were performed at baseline, 1, 3, 5, and 7 h after the theophylline dose, and 10 blood samples were collected over 9 h on both study days. The percent change of PFT from the baseline was recorded. Analysis of variance for balanced two-period crossover design was used to evaluate the effectiveness of theophylline therapy. The serum concentration (Conc.) vs. time data were fitted using nonlinear least-squares regression analysis. The theophylline dose administered was 7.9 +/- 0.4 (mean +/- SD) mg/kg, which produced a maximal Conc. (Cmax) of 14.6 +/- 2.7 microgram/ml. The half-life (T1/2), volume of distribution (Vd), and total body clearance (TBC) were 4.9 +/- 1.9 h, 537 +/- 124 mL/kg, and 80 +/- 16 ml/h/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Randomization using packaged programs

The problem of implementation of a randomization in controlled clinical trials is briefly discussed. A computer procedure is proposed and illustrated with simple programs using BMDP, SAS, and SPSS.

Determining risk for chronic otitis media with effusion

Chronic otitis media with effusion (OME) has been observed in 10 to 20% of children following acute, symptomatic otitis media. To determine factors that place children at increased risk of chronic OME, we conducted a 6-week prospective study of 386 children who had 3 or more recent episodes of otitis media and who had middle ear effusion present for at least 2 weeks. Of these children 23% developed chronic OME (i.e. effusion lasting 8 continuous weeks or more), and 26% developed chronic OME complicated by acute, symptomatic otitis media. Predictors for chronic OME were (1) bilateral OME, (2) duration of effusion for greater than 2 weeks at enrollment and (3) day care attendance. Children with these 3 factors had twice the risk of developing chronic OME as children lacking all 3 factors. These risk factors can be used to target children for early, aggressive OME therapy.

Testing for linear trends in proportions using correlated otolaryngology or ophthalmology data

This paper is concerned with the issue of testing for trend with correlated binary data. We consider the problem where one has either one or two ears (or eyes) available for analysis at baseline and one wishes to look at changes over time in a dichotomous outcome taking into account the correlation between responses from two ears. A reparameterization of Rosner's (1982, Biometrics 38, 105-114) correlated binary data model is presented and applied to a test for trend where the stratifying variable is age (or any other subject-specific variable). Observed and expected values are calculated for the trend statistic separately for both unilateral and bilateral cases and are then summed to obtain an overall summary statistic. The proposed method is illustrated by a reanalysis of data presented in a published study of the efficacy of antibiotics for the treatment of otitis media.

Computational implementation of the conditional logistic regression model in the analysis of epidemiologic matched studies

Adaptation of a BMDP packaged program for the proportional hazards survival models to the analysis of an epidemiologic matched study is discussed and illustrated with numerical examples.

Thickness of the human round window membrane in different forms of otitis media

The thickness and morphologic characteristics of the round window membrane were evaluated in temporal bones from normal subjects as well as those with serous otitis media, purulent otitis media, and chronic otitis media. Temporal bones were studied in chronological order in six age ranges to determine the possibility of age-related differences. No significant difference in the mean thickness of the round window membrane was observed in terms of age groups in normal temporal bones or temporal bones from patients with otitis media; however, a significant difference in the mean thickness was observed in the various forms of otitis media compared with the normal round window membrane in all age groups. The membrane was thickest in patients with chronic otitis media when compared with that in normal subjects or those with serous or purulent otitis media. The epithelial layer (including the subepithelial space) and the fibrous layer were measured individually to determine in which layer the change in mean thickness occurred. These measurements showed an involvement of all layers of the round window membrane in those groups with otitis media, with maximal involvement of the combined epithelial layer and subepithelial space.

Microbiological evaluation of wet and dry floor sanitization systems in hospital patient rooms

A new system for sanitizing floors in hospital patient rooms has been developed. The method consists of dry dusting with a cotton-blend, chemically treated (10% by dry mop weight) dust mop. This method was compared with a conventional cleaning protocol consisting of an initial predusting with the same nongermicidal chemical (3% by dry mop weight) followed by wet mopping with a fresh solution of a quaternary ammonium disinfectant-detergent. Each of six rooms was sampled by using RODAC plates (Becton Dickinson Labware, Oxnard, Calif.) on 10 consecutive days for each of the two methods. The study was initially performed during the summer and then repeated during the winter. Results imply that there is no significant difference between the new dry method (81.9% CFU reduction) and the conventional method (83.1% CFU reduction). Furthermore, the initial dry dusting step in the conventional method accounted for virtually all of the reduction by that method. Thus, wet mopping with a germicidal chemical produced no additional significant reduction of natural microbial populations on environmental surfaces beyond that achieved by dry dusting with dust-suppressant chemicals.