Early changes in lungs of rats exposed to 70 per cent O2.

Sixty-six respiratory disease-free rats, divided into four groups, were exposed to 70% O2 for 1.5, 4, 7, and 10 days and compared with 31 littermates exposed to room air for equal times. Lung surfactant was separated from macrophages and potential serum protein contamination by differential centrifugation of endobronchial washings. In the O2-exposed rats, developing lung edema was demonstrated by decreased dried/fresh lung weight ratio and increased alveolar protein content at 7 and 10 days. At 7 days, lung compliance slope and hysteresis loop area decreased, while critical opening pressure increased. Ultrastructurally, the only abnormality seen was an irregular widening of the alveolar capillary basement membrane on day 10. Alveolar lecithin content decreased slightly during the 10 days exposure, but remained highly saturated, whereas whole lung lecithin content increased. These results suggest that the initial mechanical and morphological alterations in rats exposed to 70% O2 are related to lung edema and are not dependent upon lung surfactant alterations.     

Early larval development and metamorphosis in the summer flounder: changes in per cent whole-body water content and effects of altered thyroid status

At the end of premetamorphosis, summer flounder Paralichthys dentatus larvae had 84·1% whole-body water content (WBW), which decreased to the lowest levels (8·5%) at the start of metamorphic climax (MC). During mid- and late MC, %WBW was slightly higher (82·1%) then returned to the lowest levels at the juvenile stage. In fish treated with thyroxine (T₄-Na salt, 100 ng ml⁻¹) beginning at premetamophosis, %WBW never differed from controls of the same age throughout metamorphosis, despite an earlier start of metamorphic climax and transitional settling behaviour. This suggests that thyroid hormones do not mediate the drop in %WBW which accompanies natural metamorphosis. Thiourea (TU, 30 μg ml⁻¹) treatment of fish over the same period induced a developmental stasis in early MC which was accompanied by initially higher %WBW than controls at 33 days post-hatch, followed by a progressive decrease to abnormally low %WBW by 42 and 45 days post-hatch. Since concurrent treatment with TU+T₄ rescued the fish from both the TU-induced developmental stasis and abnormally low %WBW, these findings suggest that thyroid hormones, or thyroid hormone-mediated developmental progression, are necessary for regulating %WBW.     

The Auxin Activity Extractable from Excised Tomato Roots by Cold 80 per cent. Methanol

Extracts of excised tomato roots prepared with cold aqueousmethanol have been partitioned between ethyl acetate and waterand chromatograms of the two fractions bioassayed by an Avenacoleoptile straight growth test and sprayed with various reagentsincluding those giving colour reactions with indole compounds.The greater part of the auxin activity is in the aqueous fractionand chromatograms of this fraction give positive indole reactions. The aqueous fraction chromatographed with isopropanol/ammonia/watershows two zones of growth-promoting activity. The zone of lowerRf contains tryptophane and unidentified ninhydrin-positivematerial. Tryptophane accounts for the activity of the Ehrlich-positiveregion of this zone. The activity of the zone of higher Rf isassociated with ninhydrin-positive material; this activity can,by use of other solvents, be distinguished in Rf from that ofthe common amino-acids which would occur in this zone on theprimary chromatograms. Chromatograms of the aqueous fractionalso show the presence of urea and of a phenol, neither of whichare associated with the zones of growth-promoting activity. The ethyl acetate fraction, and particularly the acid fractionof this, contains growth-promoting activity which, in a rangeof solvents, always corresponds in Rf to IAA. The acid fractioncontains a growth inhibitor corresponding in Rf to the ß-inhibitorof other workers. A zone of growth-promoting activity near thesolvent front on isopropanol/ammonia/water chromatograms containsmore than one active component, but IAN appears to be absent.     

Evidence that approximately eighty per cent of the soluble proteins from Ehrlich ascites cells are Nalpha-acetylated.

Analysis of soluble Ehrlich ascites proteins by the Sanger procedure revealed methionine, alanine, valine, and glycine as the major NH2-terminal amino acids. The average monomer weights of these proteins calculated from the yields of NH2-terminal amino acids was 144,000. In contrast, the average monomer weight of Ehrlich ascites soluble proteins calculated from the data obtained after electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate was 32,500. The explanation for the disparity in the estimates of average monomer weight obtained by the procedures appears to be that extensive blocking of alpha-NH2 groups by acetate occurs in these proteins, i.e. of the acetate present in the acidic peptides isolated from proteolytic digests of ascites proteins, 23.2 nmol/mg of protein appears to originate from N-acetyl amino acids. These results suggest that approximately 80% of the soluble proteins from Ehrlich ascites cells contain acetate at their NH2-terminal residues. The extensive N-acetylation of proteins does not appear to be limited to Ehrlich ascites cells and may be characteristic of eukaryotic proteins.     

Storage of ethyl methanesulphonate-treated barley seeds with 15 per cent moisture. Influence of treatment and washing conditions

Barley seeds were treated with ethyl methanesulphonate (EMS), washed for 24 h, redried to 15 per cent moisture and stored at 25°C. The criteria used for expressing the effect of storage were chromosomal aberrations in root tips, M₁ germination, M₁ seedling height, M₁ survival and the frequency of M₂ chlorophyll mutants. The increase of the M₁ biological injury due to storage was not influenced:

1. by applying EMS solutions at pH 2, pH 7 and pH 10,
2. by lowering the EMS concentration and increasing the treatment time,
3. by different variations of washing with water and by washings with 0.005 N NaOH, 200 mM cysteine or 200 mM thiourea. The rate of the increase of the M₁ injury due to storage depends on the EMS dose. With a decrease in the EMS dose the storage effect is more delayed.