Endoscopic examination of the neonatal larynx at extubation: a prospective study of variables associated with laryngeal damage.

Despite postmortem and clinical studies, the etiological factors that determine why only a proportion of intubated neonates develop subglottic stenosis remain unclear. This prospective study was initiated to identify factors that were associated with laryngeal abnormalities secondary to intubation. Thirty neonates were examined at extubation by two independent observers blinded to the neonate's ventilatory history. Thirty-six possible prognostic indicators were recorded for each neonate. After screening by univariate (chi 2) analysis, 10 indicators were selected for further analysis. Of these 10 selected only two indicators showed an association with the laryngeal appearance. Active neonates had significantly more abnormalities in the supraglottis (P = 0.004) than those who were quiescent. Younger neonates had more abnormalities in the glottis though the significance level was marginal (P = 0.056). Other prognostic indicators, including birthweight, gestational age, duration of intubation and frequency of intubation, were not significantly related to laryngeal appearance. This study supports the hypothesis that the etiology of laryngotracheal stenosis is multifactorial, and has identified two possible etiological factors: age and neonatal activity. Neonatal activity has not been identified previously as an etiological factor. The contribution of individual factors may vary from one neonatal unit to another, as a result of variation in intubation, ventilation and extubation policy. This could explain the inconsistency in etiological factors identified by previous studies. It is therefore not yet possible to recommend a standard technique for the ventilation of premature neonates that would further reduce the incidence of laryngotracheal stenosis.

Is C-reactive protein really useful in preterm premature rupture of the membranes?

In a prospective blind study 380 daily serum samples from 55 women with preterm premature rupture of the membranes were analysed for C-reactive protein (CRP). Although the last CRP before delivery was higher in patients with histological chorioamnionitis (P = 0.007), considerable overlap between infected and non-infected pregnancies occurred, precluding the use of CRP as a diagnostic test if published normal levels were used. When upper limits were set at 30, 35, or 40 mg/l, the last CRP before delivery proved 90, 95 and 100% specific and 88, 92 and 100% positively predictive of infection in singleton pregnancies. Such high specificities are needed to prevent inappropriate intervention based on false positive results. We therefore propose upper limits for single estimations of 30, 35, or 40 mg/l depending on the relative risks of preterm delivery versus infection at various gestational ages. In addition, consecutive values greater than 20 mg/l appeared highly predictive of infection.

Prolonged pregnancy: the management debate.

A prospective trial was conducted to compare the effects of conservative management of prolonged pregnancy (conservative group) with routine induction of labour at 42 weeks' gestation (active group) in otherwise uncomplicated pregnancies. Of the 402 pregnancies studied, 207 (51%) were allocated to conservative management and 195 (49%) were allocated to have labour induced. The groups were well matched for age, parity, and smoking habits. One hundred and sixty six (80%) of the patients in the conservative group went into spontaneous labour. Of the remainder, two underwent elective caesarean section, 19 had labour induced because of clinical concern, and the remaining 20 had labour induced at the patient's own request. One hundred and twenty five (64%) of the patients in the planned active group underwent induction of labour. Of the remaining 70, 49 went into spontaneous labour and 21 (11%) asked that they should not have labour induced. Comparison of the two groups showed no difference in the length of the first stage of labour but a trend towards an increased need for intervention for fetal distress (p less than 0.06) in the active group. There were no differences in the length of the second stage, the need for intervention, or the mode of delivery. In terms of Apgar scores the neonatal outcome was not significantly different between the two groups, but a greater proportion of the babies (15% v 8%) in the active group required intubation. Umbilical cord venous pH estimated in the last 183 consecutive deliveries in the study showed a significantly lower mean value in the active group (p less than 0.05). There was no difference in birth weight between the two groups. Two deaths occurred in the study. There was a stillbirth in the conservative group at 292 days after massive abruption, and one neonatal death in the active group owing to multiple congenital abnormalities. The outcome for mother and baby in patients from both groups who went into spontaneous labour was generally good. The outcome for patients for whom conservative management was planned but induction became necessary was no different from that of patients who underwent planned induction at term. Thus from our results we can find no evidence to support the view that women with normal prolonged pregnancy should undergo routine induction of labour at 42 weeks' gestation.

Androgen receptor-mediated genetic differences in 2-acetylaminofluorene and dimethylnitrosamine mutagenesis in vitro.

When 2-acetylaminofluorene and dimethylnitrosamine mutagenesis rates in the Salmonella/liver in vitro system were studied with C3H/HeJ mouse kidney or liver postmitochondrial supernatant (S-9) fractions, sex differences (male much greater than female) of 10- to 30-fold were found in kidney but not liver. We examined male mice castrated during the neonatal period, the Tfm/Y male, and dihydrotestosterone-treated female mice. The requirement of both testosterone and the androgen receptor is shown to be important in causing the sex difference in 2-acetylaminofluorene and dimethylnitrosamine mutagenesis in the kidney. Swank et al. [J Mol Biol 81:225-243 (1973)] demonstrated that dihydrotestosterone induces beta-glucuronidase activity in the female kidney: 28- to 30-fold in BALB/cJ and SM/J, 12-fold in C3H/HeJ, and 5- to 6-fold in C57BL/6J and RF/J inbred mice. This gene regulation has been characterized and named the Gur locus. 2-Acetylaminofluorene mutagenesis--in kidney but not liver--is markedly enhanced by dihydrotestosterone (P less than 0.01) in the first three, but not the latter three, inbred strains. Covalent binding of 2-acetylaminofluorene metabolites to DNA in the presence of kidney S-9 fractions in vitro is greatly increased in the BALB/cJ but not C57BL/6J female mouse pretreated with dihydrotestosterone. These data suggest that genetic differences at the Gur locus, in combination with the androgen receptor, may play an important role in the sex-specific and tissue-specific conversion of an O-glucuronide of N-hydroxy-2-acetylaminofluorene or N-hydroxy-aminofluorene to active mutagenic intermediates.

Relationship of metabolic activation of N-hydroxy-N-acylarylamines to biological response in the liver and mammary gland of the female CD rat.

Intraperitoneal injection of the N-formyl, N-acetyl, or N-propionyl derivatives of N-hydroxy-4-aminobiphenyl, N-hydroxy-2-acetylaminofluorene, or N-(4-biphenyl)glycolamide disclosed that the ability of these compounds to induce mammary tumors in the female CD rat was greater if the compound was able to be metabolized to a reactive product by one of two soluble enzymes obtained from both the liver and mammary gland. A similar but weaker association between the formation of gamma-glutamyltranspeptidase-positive foci and cellular altered foci of the liver was also observed. The enzyme related to the tumorigenicity of these compounds was characterized by a highly specific capacity to form adducts from the acetyl and propionyl derivatives. The other enzyme exhibited greater activity with N-formyl substrates. The two enzyme activities were separable by ion-exchange chromatography on DEAE-cellulose and by gel filtration on Sephacryl. Liver microsomes also possessed the capacity to activate both the formyl and acetyl derivatives to reactive species; formyl substrates were 7 to 8 times more active than acetylated compounds. The microsomal activities and the formyl-preferring soluble enzyme were inhibited by diethyl-p-nitrophenylphosphate, a microsomal deacylase inhibitor. The cytosolic enzymes that are most active with the acetyl and propionyl substrates were little affected by this organophosphate compound. The microsomal activation was not due solely to deacylation of the hydroxamic acid, since formylated and acetylated substrates were hydrolyzed at approximately the same rates.

Evidence that arylhydroxamic acid N,O-acyltransferase and the genetically polymorphic N-acetyltransferase are properties of the same enzyme in rabbit liver.

Arylhydroxamic acid N,O-acyltransferase and Co-ASAc-dependent N-acetyltransferase activities were measured simultaneously in liver cytosols from rabbits of known acetylator phenotype. Both activities were high in rapid acetylator rabbits and low in slow acetylator rabbits indicating that these two acetyl transfer steps in the metabolic activation of certain arylamines are under common genetic control in this species. The two enzyme activities could not be resolved by sequential centrifugation, fractional precipitation with ammonium sulfate, ion exchange chromatograhy on DEAE-cellulose, gel filtration on Sephacryl, and electrophoresis on polyacrylamide gels. Sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis of extracts of disc gel electrophoretic slices showed that a single symmetrical protein band with a molecular weight of 33,000 was associated with both activities. The results obtained strongly suggest that the CoASAc-dependent N-acetyltransferase reaction and the intramolecular N,O-acetyl transfer by arylhydroxamic acid N,O-acyltransferase are properties of the same enzyme.

Comparison of hexachlorophane and chlorhexidine powders in prevention of neonatal infection.

The protective effect of treating the skin of newborn infants with powders containing 1% chlorhexidine or 0.33% hexachlorophane was compared. Each was equally effective in preventing colonisation and infection by Staphylococcus aureus. In contrast, the skin became profusely colonised by coagulase-negative staphylococci, irrespective of the powder used. Venous blood concentrations of chlorhexidine were low or undetectable in the few infants whose blood was analysed.

Differing degrees of coal-tar shampoo-induced mutagenesis in the Salmonella/liver test system in vitro.

Hexane extracts of four commercial preparations of coal tar shampoos were studied for their mutagenic properties in the Salmonella/liver test system in vitro. Three of the four shampoos were highly mutagenic, whereas the fourth was not - under our experimental conditions. By high-performance liquid chromatographic, gas-liquid chromatographic, and gas-liquid chromatography-mass spectrometric analyses, more than 35 distinct fractions could be resolved; seven polycyclic aromatic chemicals believed to be present in coal tar were tentatively assigned as the major component of some of these fractions. The shampoo extract that was most mutagenic had a greater number of distinct fractions and contained approximately 50 times more benzo[a]pyrene, compared with the one shampoo extract that was not mutagenic under our experimental conditions. The possible clinical hazards of this observed mutagenicity of certain coal tar shampoos are presently not known.

The Ah locus: biochemical basis for genetic differences in brain tumor formation in mice.

Allelic differences at the Ah locus are showen to exist in the mouse brain. This finding probably explains inbred mouse strain differences in polycyclic hydrocarbon tumorigenesis of the brain described more than 35 years ago and may be important in understanding the etiology of genetic differences in certain human intracranial neoplasms.

2,3,7,8-Tetrachlorodibenzo-p-dioxin: covalent binding of reactive metabolic intermediates principally to protein in vitro.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is metabolized by the mouse liver cytochrome P-450-mediated monooxygenase system to reactive intermediates which bind 'covalently' to cellular macromolecules. Although very difficult to quantitate, the presumably covalent binding to microsomal protein occurs between 120 and 2,640 times more readily than binding to deproteinized DNA in the in vitro reaction. Because of the extremely high rate of binding to protein rather than to DNA, it is visualized that TCDD metabolites may be so reactive that they bind in or near the P-450-active site where the TCDD is monoxygenated. This extreme reactivity may preclude the formation of detectable quantities of phenols, dihydrodiols, or conjugated products. The rate of TCDD metabolism is estimated to be between 9,000 and 36,000 times lower than the rate of P-450-mediated benzo[a]pyrene metabolism. To our knowledge, this is the first demonstration that TCDD is metabolized in any organism. There remains the possibility, however unlikely, that this covalently-bound radioactivity represents metabolites of contaminants--present in the radiolabeled TCDD sample in very minute amounts--rather than metabolites of tritiated TCDD itself. The possible relationship between P-450-mediated metabolism of this environmental contaminant and its extreme toxicity or teratogenicity is discussed.