Adenosine dimethylation of 16S ribosomal RNA: effect of the methylgroups on local conformational stability as deduced from electrophoretic mobility of RNA fragments in denaturing polyacrylamide gels.

The electrophoretic mobility of RNA fragments derived from the 3'-end of 16S rRNA on slabs of polyacrylamide gel in the presence of urea is strongly influenced by dimethylation of the N6-aminogroup of two adjacent adenosines. This is not due to the presence of the methylgroups per se, but must be ascribed to an effect of methylation on long range intramolecular interactions at these denaturing conditions. When it is assumed that the electrophoretic mobilities of the RNA fragments in the polyacrylamide matrix are determined by the conformational state(s) of the fragments, dimethylation of the adenosines leads in the smaller fragments to a less compact average conformation and in the larger fragments to a more compact average conformation. An effort is made to comprehend the effects of adenosine dimethylation in terms of secondary structure based on nucleotide sequence.     

Prolactin levels and the LH-response to synthetic LH-RH in the lactating sow

To determine the role of prolactin in the suppression of ovarian activity during lactation in the sow experiments were performed to investigate a possible inhibitory action of prolactin at the pituitary level. Therefore the LH-response to an intravenous injection of 25 μg synthetic LH-RH was measured in the 1st, 2nd and 3rd week of lactation. The compound was injected under high and low concentrations of prolactin in the peripheral blood, the latter achieved by removal of the piglets 6 h before administration of LH-RH. The results showed no difference in the effect of LH-RH injected at high or low prolactin levels. However, although the mean prolactin concentrations in the 1st, 2nd and 3rd week of lactation were similar, the results clearly demonstrated an increase in LH-response as lactation proceeds.The low responsiveness of the pituitary shortly post partum was also observed when the preparturient rise of prolactin was suppressed by treatment with bromoergocryptine. Injections of LH-RH in the last week of gestation given before and after the physiological increase of PRL, which occurred about 48 h before delivery, all showed low LH-response.It is obvious from the presented data that the LH-response to an intravenous injection of 25 μg LH-RH is in no way correlated with the prolactin levels at the time of treatment.     

Determination of plasma theophylline by straight-phase high-performance liquid chromatography: Elimination of interfering caffeine metabolites

Several authors have recently reported interference in theophylline analysis by paraxanthine (1,7-dimethylxanthine), an important metabolite of caffeine. A method for the determination of theophylline in plasma is described, eliminating caffeine and related compounds by means of straight-phase high-performance liquid chromatography. The resulting procedure is sufficiently rapid, accurate and sensitive to be applied in routine monitoring of therapeutic levels in patients as well as for pharmacokinetic purposes. Although only 0.1 ml of sample is required, concentrations as low as 0.2 mg/l can be measured with acceptable precision. A brief comparative evaluation of this procedure with a radioimmunoassay is made.     

Energy conservation during nitrate respiration in Paracoccus denitrificans

P/2e ratios were calculated from anaerobic chemostat cultures of Paracoccus denitrificans with nitrogenous oxides as electron acceptor. P/2e ratios were calculated, using the Y _ATP ^max values determined for aerobic cultures. When succinate was the carbon and energy source the average P/2e values of the sulphate-and succinate-limited cultures with nitrate as electron acceptor were 0.5 and 0.7, respectively, and of the nitrite-limited culture 0.9. With gluconate as carbon and energy source the average P/2e values of the gluconate-limited with nitrate as electron acceptor and nitrate limited cultures were 0.9 and 1.1, respectively.H⁺/O ratios measured in cells obtained from sulphate-, succinate, nitrite-, gluconate-and nitratelimited cultures yielded respective average values of 3.4, 4.5, 3.5, 4.8 and 6.2 for endogenous substrates. From our data we conclude that sulphate-and nitritelimitation causes the loss of site I phosphorylation. Nitrite has no influence on the maximum growth yield on ATP. We propose that metabolism in heterotrophically grown cells of Paracoccus dentrificans is regulated on the level of phosphorylation in the site I region of the electron transport chain.     

Partial trisomy 14q due to familial t(14q-, 11q+) translocation

Summary A malformed male newborn with partial trisomy for the distal part of the long arm chromosome 14 (14q₂₃14qter) is described. This anomaly arose as a segregation product of a balanced t(14q-, 11q+), translocation in the father.     

Fructose metabolism in four Pseudomonas species

1. ATP-Dependent phosphorylation of fructose could not be detected in extracts of fructose-grown cells of Pseudomonas extorquens strain 16, Pseudomonas 3A2, Pseudomonas acidovorans and Pseudomonas fluorescens. Instead, phosphorylation of fructose to fructose-1-phosphate was found to occur when cell-free extracts were incubated with fructose and phosphoenolpyruvate. Such an activity could not be detected in cell-free extracts of succinate-grown cells. 2. High levels of 1-phosphofructokinase were found in extracts of the above organisms when growth on fructose. 3. Mutants of Pseudomonas extorquens strain 16 lacking 1-phosphofructokinase were unable to grow on fructose. Revertants to growth on fructose had regained the capacity to synthesize this enzyme, indicating its necessary involvement in fructose metabolism. 4. A survey has been carried out of enzymes involved in carbohydrate metabolism in the species listed above.