Comparison of two tests and absorbance at 650 nm for assessing fetal lung maturity

The clinical performance of three rapidly performed tests--tap test, TDx Fetal Lung Maturity and amniotic fluid absorbance at 650 nm--in predicting fetal lung maturity were evaluated in 300 samples of clear amniotic fluid. In all cases, delivery occurred within three days of sample collection. Of the 300 newborns, 44 developed respiratory distress syndrome. For the tap test, the sensitivity (95.4%), specificity (82.8%), and predictive value for maturity (99.7%) and immaturity (48.9%) were comparable to those of the TDx fetal lung maturity test: sensitivity of 100%, specificity of 88.3%, and predictive value for maturity of 100% and immaturity of 53.1%. The specificity (68.4%) and predictive value for immaturity (34.7%) of amniotic fluid absorbance at 650 nm were significantly lower than for the TDx and tap tests, whereas no significant difference was found for sensitivity and prediction of maturity between amniotic fluid absorbance at 650 nm and the TDx and tap tests. Both the tap and the TDx tests appear to be useful in antenatal assessment of fetal lung maturity in terms of reliability, rapidity and uniformity.     

Turbulent/viscous interactions control Doppler/catheter pressure discrepancies in aortic stenosis. The role of the Reynolds number

BACKGROUND: Despite good correlation between Doppler and catheter pressure drops in numerous reports, it is well known that Doppler tends to apparently overestimate pressure drops obtained by cardiac catheterization. Neither (1) simplification of the Bernoulli equation nor (2) pressure recovery effects can explain this dilemma when taken alone. This study addressed the hypothesis that a Reynolds number-based approach, which characterizes (1) and (2), provides a first step toward better agreement of catheter and Doppler assessments of pressure drops. METHODS AND RESULTS: Doppler and catheter pressure drops were studied in an in vitro model designed to isolate the proposed Reynolds number effect and in a sheep model with varying degrees of stenosis. Doppler pressure drops in vitro correlated with the directly measured pressure drop for individual valves (r = .935, .960, .985, .984, .989, and .975) but with markedly different slopes and intercepts. A Bland-Altman type plot showed no useful pattern of discrepancy. The Reynolds number was successful in collapsing the data into the profile proposed in the hypothesis. Parallel results were found in the animal model. CONCLUSIONS: Apparent overestimation of net pressure drop by Doppler is due to pressure recovery effects, and these effects are countered by both viscous effects and inertial/turbulent effects. Only by reconciliation of discrepancies by use of a quantity such as Reynolds number that embodies the relative importance of competing factors can the noninvasive and invasive methods be connected. This study shows that a Reynolds number-based approach accomplishes this goal both in the idealized in vitro setting and in a biological system.     

Analysis of testosterone esters by tandem mass spectrometry

OBJECTIVE: To assess the efficacy of external cephalic version, including safety, cost-benefit analysis, and impact on the cesarean delivery rate. DATA SOURCES: A MEDLINE search was conducted to identify all articles published in English between 1980-1991 on external cephalic version. References were also cross-checked for all reports. METHODS OF STUDY SELECTION: We reviewed only those articles providing sufficiently detailed data to determine actual numbers of subjects. In cases of duplicate results, only the latest publication was used. Rates of successful version, cesarean delivery, and fetal and maternal complications were presented. DATA EXTRACTION AND SYNTHESIS: Among the United States trials, the success rate was approximately 65% (range 48-77%), and once version succeeded, almost all the fetuses stayed in the vertex position until birth. Among those in whom external version was performed, the mean cesarean delivery rate was 37%, compared with 83% in controls (P < .001). External version would also save 12.3% of the costs of delivering breech patients overall. CONCLUSION: External cephalic version is safe and cost-effective. It substantially reduces the cesarean delivery rate among breech presentations, decreases the risk related to breech delivery, and avoids cesarean delivery in subsequent pregnancies. However, external version will not have a major impact on the high overall cesarean birth rate.     

Socioeconomic disadvantage, proximal environmental experiences, and socioemotional and academic adjustment in early adolescence: investigation of a mediated effects model

This study investigated interrelations among conditions of household socioeconomic disadvantage, proximal environmental experiences, and adaptational outcomes in a sample of 398 middle grade, early adolescents from a predominantly poor, rural area. Findings indicated that levels of disadvantage were related to both socioemotional and academic adjustment, with those from relatively disadvantaged backgrounds faring most poorly. Specifically, youth from homes in which adults were employed in low-income, unskilled occupations were found to have lower levels of school performance and achievement compared to those from homes in which adults were employed in higher paying semi-skilled or skilled/professional occupations. Further, youth from families in which neither parent had graduated from high school exhibited significantly worse socioemotional and academic adjustment than did those whose parents had higher educational levels. Youth who lived in relatively disadvantaged homes also reported more negative experiences of proximal environmental conditions relating to family and school contexts and greater exposure to stressful life events. Most notably, findings provided support for employing an ecological-mediational perspective to understand patterns of linkage between socioeconomic disadvantage and levels of adjustment. Support for this viewpoint included the finding that proximal environmental experiences were significant predictors of adolescent adjustment, independent of shared variance with conditions of household disadvantage, whereas conditions of disadvantage in several instances were no longer related significantly to indices of adjustment once their association with proximal environmental conditions was taken into account. The discussion considers implications for the targeting and scope of ecologically oriented approaches to preventive intervention.     

Experimental evaluation of two simple thermal models using hyperthermia in muscle in vivo

The predictions from two simple field equation models for calculating temperature distributions in tissue, namely, the Pennes' bioheat transfer equation (BHTE) and an effective thermal conductivity equation (ETCE), were compared to in vivo experimental temperature measurements made under hyperthermic conditions generated by scanned focused ultrasound. The models were kept simple (i.e. homogenous isotropic properties, no separate blood vessels included) in order to concentrate attention on the predictive abilities of these field equations using a minimum number of free parameters. Simulated results were fitted to the experimental data (multiple, linear temperature profiles in the thigh muscles of greyhound dogs) by minimizing a performance index using a golden section searth. This search determined a value for the single free parameter in each model (blood perfusion in the BHTE, and effective thermal conductivity in the ETCE) which minimized the square error difference between the experimental and simulated temperatures. The results showed that (a) the simple BHTE model could qualitatively reproduce the major features of the temperature patterns seen experimentally better than the ETCE model could, and (b) the simple BHTE model produced better quantitative fits to the experimental data than did the simple ETCE model. In addition, blood perfusion predictions from the BHTE model compared well to measurements done with coloured microspheres. Finally, the experimental results showed that individual, large blood vessels appeared to have a major influence in producing asymmetries in the experimental data in 21% of the measured temperature profiles.     

Effects of misoprostol on pentylenetetrazol-induced seizures in mice

The effects of prostaglandin E-analogue misoprostol on the susceptibility to pentilenetetrazol (PTZ)-induced seizures were examined in mice. Misoprostol (200-800 micrograms/kg), given subcutaneously 45 min before the subconvulsive dose of PTZ (30 mg/kg, i.p) provoked dose-dependent clonic-tonic seizures (30 to 100%) and mortality in mice. At 300 g/kg, s.c., misoprostol pretreatment significantly (p < 0.05) lowered the onset latency to first convulsion as well as the latency to mortality induced by a convulsive dose of PTZ (60 mg/kg, i.p.). At this dose misoprostol was found to lower the CD50 and Ld50 values for PTZ by 21% and 36% respectively. The results suggest that prostaglandins are likely to lower the threshold for convulsions.     

Ultrastructure of Kunjin virus-infected cells: colocalization of NS1 and NS3 with double-stranded RNA, and of NS2B with NS3, in virus-induced membrane structures

The subcellular location of the nonstructural proteins NS1, NS2B, and NS3 in Vero cells infected with the flavivirus Kunjin was investigated using indirect immunofluorescence and cryoimmunoelectron microscopy with monospecific antibodies. Comparisons were also made by dual immunolabelling using antibodies to double-stranded RNA (dsRNA), the putative template in the flavivirus replication complex. At 8 h postinfection, the immunofluorescent patterns showed NS1, NS2B, NS3, and dsRNA located in a perinuclear rim with extensions into the peripheral cytoplasm. By 16 h, at the end of the latent period, all patterns had changed to some discrete perinuclear foci associated with a thick cytoplasmic reticulum. By 24 h, this localization in perinuclear foci was more apparent and some foci were dual labelled with antibodies to dsRNA. In immuno-gold-labelled cryosections of infected cells at 24 h, all antibodies were associated with clusters of induced membrane structures in the perinuclear region. Two important and novel observations were made. First, one set of induced membranes comprised vesicle packets of smooth membranes dual labelled with anti-dsRNA and anti-NS1 or anti-NS3 antibodies. Second, adjacent masses of paracrystalline arrays or of convoluted smooth membranes, which appeared to be structurally related, were strongly labelled only with anti-NS2B and anti-NS3 antibodies. Paired membranes similar in appearance to the rough endoplasmic reticulum were also labelled, but less strongly, with antibodies to the three nonstructural proteins. Other paired membranes adjacent to the structures discussed above enclosed accumulated virus particles but were not labelled with any of the four antibodies. The collection of induced membranes may represent virus factories in which translation, RNA synthesis, and virus assembly occur.     

Identification of a new inborn error in bile acid synthesis: mutation of the oxysterol 7alpha-hydroxylase gene causes severe neonatal liver disease

We describe a metabolic defect in bile acid synthesis involving a deficiency in 7alpha-hydroxylation due to a mutation in the gene for the microsomal oxysterol 7alpha-hydroxylase enzyme, active in the acidic pathway for bile acid synthesis. The defect, identified in a 10-wk-old boy presenting with severe cholestasis, cirrhosis, and liver synthetic failure, was established by fast atom bombardment ionization-mass spectrometry, which revealed elevated urinary bile acid excretion, a mass spectrum with intense ions at m/z 453 and m/z 510 corresponding to sulfate and glycosulfate conjugates of unsaturated monohydroxy-cholenoic acids, and an absence of primary bile acids. Gas chromatography-mass spectrometric analysis confirmed the major products of hepatic synthesis to be 3beta-hydroxy-5-cholenoic and 3beta-hydroxy-5-cholestenoic acids, which accounted for 96% of the total serum bile acids. Levels of 27-hydroxycholesterol were > 4,500 times normal. The biochemical findings were consistent with a deficiency in 7alpha-hydroxylation, leading to the accumulation of hepatotoxic unsaturated monohydroxy bile acids. Hepatic microsomal oxysterol 7alpha-hydroxylase activity was undetectable in the patient. Gene analysis revealed a cytosine to thymidine transition mutation in exon 5 that converts an arginine codon at position 388 to a stop codon. The truncated protein was inactive when expressed in 293 cells. These findings indicate the quantitative importance of the acidic pathway in early life in humans and define a further inborn error in bile acid synthesis as a metabolic cause of severe cholestatic liver disease.