Crown-rump length discordance in the first trimester: a predictor of adverse outcome in twin pregnancies?

OBJECTIVES: To evaluate the usefulness of first-trimester crown-rump length (CRL) discordance in predicting adverse outcome in twin pregnancies. METHODS: This retrospective study included a large cohort retrieved from local ultrasound databases at 14 obstetric departments in Denmark, comprising all twin pregnancies with two live fetuses scanned between 11 and 14 weeks' gestation during the period 1 January 2004 to 31 December 2006. The association between CRL discordance ≥ 10 % and adverse outcome was evaluated. RESULTS: Among 1993 twin pregnancies, 1733 were dichorionic (156 (9%) discordant; 1577 (91%) concordant) and 260 were monochorionic (32 (12%) discordant; 228 (88%) concordant). In dichorionic twin pregnancies we found an association between CRL discordance ≥ 10% and preterm delivery before 34 weeks' gestation (P=0.007), birth weight discordance (P=0.001) and mean birth weight (P=0.033). In monochorionic twin pregnancies we found an association between CRL discordance ≥ 10% and birth weight discordance (P=0.02) and mean birth weight (P=0.03). To evaluate CRL discordance as a predictor of fetal loss and preterm delivery before 34 weeks' gestation, receiver-operating characteristics curves were created for each outcome. For CRL discordance ≥ 10% as a predictor of fetal loss and preterm delivery in dichorionic twin pregnancies, sensitivity was 0.17 (95% CI, 0.06-0.28) and 0.14 (95% CI, 0.10-0.18), respectively, and in monochorionic twin pregnancies it was 0.10 (95% CI, 0.03-0.22) and 0.16 (95% CI, 0.06-0.26), respectively. CONCLUSIONS: CRL discordance in twin pregnancies is associated with, but is not a strong predictor of, adverse outcome.

Mutagenic action of methyl 2-cyanoacrylate vapor.

Alkyl 2-cyanoacrylate adhesives were tested for mutagenicity in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1538. Both a normal spot test and a spot test specially designed to test volatile compounds were used. The adhesives were also tested in the plate incorporation assay. These investigations showed that methyl 2-cyanoacrylate adhesives are mutagenic in strain TA100. The spot test for volatile compounds showed that it is the vapors from the methyl 2-cyanoacrylate monomer that are responsible for the mutagenic effect. One can conclude that working with methyl 2-cyanoacrylate adhesives entails exposure to vapors with a mutagenic effect and may therefore pose a carcinogenic hazard. Because the adhesives are used in industry, their mutagenic effect has a special importance in work environment.

Involvement of Na+-K+-ATPase in p-aminohippurate transport by rabbit kidney tissue.

1. The relation between renal accumulation of p-aminohippurate (PAH), Na+-K+-ATPase activity, and the transmembranal Na+ gradient has been investigated by the use of cortex slices of rabbit kidney. 2. A moderate stimulation of PAH uptake rate was observed under anaerobic conditions in the presence of an extracellular-to-intracellular directed gradient of Na+. 3. Inhibition of aerobic accumulation of PAH by ouabain was related to a decrease in Na+-K+-ATPase activity, as evidenced by changes in tissue concentrations of Na+ and K+ and by measurements of high-affinity binding of ouabain to the slices. 4. Accumulation of PAH in media with various concentrations of Na+ and K+ resembled the effect of the cations on the ATPase activity of an isolated preparation of Na+-K+-ATPase. 5. Counteraction of the inhibitory effect of ouabain on PAH accumulation by a high concentration of K+ in the medium was related to retention of Na+-K+-ATPase activity, as evidenced by preservation of tissue--medium gradients of Na+ and K+. 6. The present data provide strong evidence for the involvement of Na+-K+-ATPase in the energization of renal PAH accumulation. However, it appears probable that a metabolic (Na+-gradient-independent) component, in addition to a Na+ gradient, is essential for the attainment of high accumulation ratios of PAH by intact renal cells.

An energy-dependent, sodium-independent component of active p-aminohippurate transport in rabbit renal cortex.

1. The relation between the coupling of metabolic energy to renal p-aminohippurate (PAH) accumulation and Na+-K+ transport was studied in rabbit cortical slices. 2. Cyanide (CN-), 2,4-dinitrophenol (DNP) and fluoride (F-( at low-medium concentrations, giving rise to a slight decline of tissue ATP concentration, caused a reduction o PAH accumulation without significantly affecting intracellular Na+ and K+ concentrations. However, higher levels of the metabolic inhibitors also resulted in considerable inhibition of active Na+-K+ transport. 3. The rate of carrier-mediated PAH uptake was slow under anaerobic conditions, relative to that measured under aerobic conditions in Na+-depleted slices. In the latter case the maximal accumulation achieved was only 1.55 +/- 0.16. 4. The uptake rate of PAH under anaerobic conditions was not inhibited by the absence of Na+ or addition of metabolic inhibitors in the concentrations used under aerobic conditions. 5. It is concluded that although Na+ is required for the attainment of high accumulation ratios of PAH, oxidative metabolism stimulates PAH flux by a Na+-independent mechanism.

Kinetics of p-aminohippurate transport in rabbit kidney slices. Role of Na+.

Active accumulation of p-aminohippurate by cortex slices of rabbit kidney in vitro requires 2.5-3 h at 25 degrees C to attain a steady-state value. The uptake process can be divided into a rapid and a slow component. The slow component makes the largest contribution to the final accumulation of p-aminohippurate. Rapid uptake is dependent on oxidative metabolism, but is not affected by Na+ or ouabain. By way of contrast, Na+ is required for the slow uptake process to occur. Efflux of p-aminohippurate accumulated in the presence of Na+ is stimulated by transfer to media with a low concentration of Na+. On the other hand, there is only evidence of a stimulatory effect of Na+ on p-aminohippurate influx at medium concentrations above 30 mM. The results indicate the existence of both Na+-dependent and Na+-independent p-aminohippurate transport, respectively.

Mutagenic action of isocyanates used in the production of polyurethanes.

Isocyanates used in the production of polyurethanes were investigated for mutagenic action in Salmonella typhimurium. These investigations showed that the most commonly used isocyanates, toluene diisocyanate (TDI) and 4,4'-methylene-diphenylisocyanate (MDI), are mutagenic. This effect can be ascribed to the amine analogues formed during the hydrolysis of isocyanates: TDI is mutagenic in TA 1538 and TA 98 after metabolic activation. This finding agrees with the results obtained with the amine analogue 2,4-toluenediamine. MDI, like the amine analogue 4,4'-methylenedianiline, is mutagenic in TA 100 after metabolic activation by rat liver enzymes (S-9 mix). A prepolymerized polyisocyanate of the MDI type is also mutagenic in assays using TA 100 and S-9 mix. It is concluded that isocyanates are potentially mutagenic and carcinogenic to man. In view of their widespread use in the work environment and in light of the high production figures for polyurethanes in industrialized countries, isocyanates must be considered to represent a serious health hazard.

Kinetics studies on the renal transport of probenecid in vitro.

1. The kinetic parameters of renal transport of probenecid have been assessed by studying the uptake of the drug in rabbit kidney tubules incubated in an electrolyte medium under various conditions. 2. The added compounds inhibited the uptake of probenecid both by kidney cortical slices and separated renal tubule preparations in the following order: p-aminohippurate less than phenol red less than bromophenol blue less than bromocresol green. A reversible competitive inhibitory effect of these organic anions on the renal accumulation of the drug was observed. 3. The Km for renal uptake of probenecid in separated tubules (0.04 mM) and the KI values calculated in this system for p-aminohippurate (0.5 mM), phenol red (0.09 mM), bromophenol blue (0.02 mM) and bromocresol green (0.015 mM) were found to be in good agreement with the corresponding KI value of probenecid and Km values of these compounds previously observed in various kidney tissue preparations. 4. On the basis of above mentioned findings, it is concluded that probenecid, p-aminohippurate and various phenolsulphonphthalein dyes are transported by the common renal organic anion transport system.

Mutagenicity of fume particles from metal arc welding on stainless steel in the Salmonella/microsome test.

Mutagenic activity of fume particles produced by metal arc welding on stainless steel (ss) is demonstrated by using the Salmonella/microsome mutagenicity test described by Ames et al., with strain TA100 (base-pair substitution) and TA98 (frame-shift reversion). Results of a representative but limited selection of processes and materials show that mutagenic activity is a function of process and process parameters. Welding on stainless steel produces particles that are mutagenic, whereas welding on mild steel (ms) produces particles that are not. Manual metal arc (MMA) welding on stainless steel produces particles of higher mutagenic activity than does metal inert gas (MIG) welding, and fume particles produced by MIG welding under short-arc transfer. Further studies of welding fumes (both particles and gases) must be performed to determine process parameters of significance for the mutagenic activity.