Organization of the ribosomal ribonucleic acid genes in various wild-type strains and wild-collected strains of Neurospora

Summary The organization of the ribosomal DNA (rDNA) repcat unit in the standard wild-type strain of Neurospora crassa, 74-OR23-1A, and in 30 other wild-type strains and wild-collected strains of N. crassa, N. tetrasperma, N. sitophila, N. intermedia, and N. discreta isolated from nature, was investigated by restriction enzyme digestion of genomic DNA, and probing of the Southern-blotted DNA fragments with specific cloned pieces of the rDNA unit from 74-OR23-1A. The size of the rDNA unit in 74-OR23-1A was shown to be 9.20 kilobase pairs (kb) from blotting data, and the average for all strains was 9.11+0.21 kb; standard error=0.038; coefficient of variation (C.V.)=2.34%. These data indicate that the rDNA repeat unit size has been highly conserved among the Neurospora strains investigated. However, while all strains have a conserved HindIII site near the 5 end of the 25 S rDNA coding sequence, a polymorphism in the number and/or position of HindIII sites in the nontranscribed spacer region was found between strains. The 74-OR23-1A strain has two HindIII sites in the spacer, while others have from 0 to at least 3. This restriction site polymorphism is strain-specific and not species-specific. It was confirmed for some strains by restriction analysis of clones containing most of the rDNA repeat unit. The current restriction map of the 74-OR23-1A rDNA repeat unit is presented.     

Prostaglandin 12 reduces activation of human arterial smooth muscle cells in-vivo

Patients suffering from peripheral vascular disease have been “ultima ratio”-treated with PGI2 at a rate of 5 ng/kg/min for 6 hours a day and 5 consecutive days i.v. 20 of them underwent surgery thereafter as therapy was not sufficient. A histological examination and quantification of vascular tissue revealed that the number of activated smooth muscle cells was significantly lower in treated patients vascular segments than in untreated ones in all the different age groups. A comparable suppression was found in the intima and the media as well. It is thus concluded, that PGI2 inhibits smooth muscle cell proliferation most probably by inhibiting PDGF-release from the platelets and stimulation of smooth muscle cell cAMP. To achieve a more beneficial PGI2-effect at the vascular level, a prolonged PGI2-therapy looks rather promising.     

Reproducibility of the multiple inert gas elimination technique

Although measurement errors in the multiple inert gas elimination technique have a coefficient of variation of approximately 3%, small biological fluctuations in ventilation, blood flow, or other variables must contribute additional variance to this method of assessing ventilation-perfusion (VA/Q) mismatch. To determine overall variance of computed indices of VA/Q mismatch, an analysis of variance was carried out using a total of 400 duplicate pairs of inert gas samples obtained from canine (N = 118) and human (N = 282) studies in the past 2 years. In both sets VA/Q mismatch ranged from minimal (2nd moment of ventilation and blood flow distributions, log SDV and log SDQ, respectively approximately equal to 0.3 each) to severe (log SDV and log SDQ approximately equal to 2.0). Differences between duplicate log SD values were computed and found to be a constant fraction of the mean log SD of each duplicate pair, averaging 13% for both canine and human ventilation and blood flow data. The resultant coefficient of variation for a single measurement of log SD about its mean averaged 8.6% for all data combined. This analysis demonstrates excellent reproducibility of these dispersion indices over a wide range of conditions, and if the mean of duplicate values is used, thus reducing variability by square root 2 to 6.1%, log SD can be estimated with an approximately 95% confidence limit of +/- 12%.     

Comparison of direct and indirect measurements of pulmonary capillary transit times

Using in vivo microscopy, we made direct measurements of pulmonary capillary transit time by determining the time required for fluorescent dye to pass from an arteriole to a venule on the dependent surface of the dog lung. Concurrently, in the same animals, pulmonary capillary transit time was measured indirectly in the entire lung using the diffusing capacity method (capillary blood volume divided by cardiac output). Transit times by each method were the same in a group of five dogs [direct: 1.75 +/- 0.27 (SE) s; indirect: 1.85 +/- 0.33 s; P = 0.7]. The similarity of these transit times is important, because the widely used indirect determinations based on diffusing capacity are now shown to coincide with direct measurements and also because it demonstrates that measurements of capillary transit times on the surface of the dependent lung bear a useful relationship to measurements on the capillaries in the rest of the lung.     

Linear programming analysis of VA/Q distributions: average distribution

The defining equations of the multiple inert gas elimination technique are underdetermined, and an infinite number of VA/Q ratio distributions exists that fit the same inert gas data. Conventional least-squares analysis with enforced smoothing chooses a single member of this infinite family whose features are assumed to be representative of the family as a whole. To test this assumption, the average of all ventilation-perfusion ratio (VA/Q) distributions that are compatible with given data was calculated using a linear program. The average distribution so obtained was then compared with that recovered using enforced smoothing. Six typical sets of inert gas data were studied. In all sets but one, the distribution recovered with conventional enforced smoothing closely matched the structure of the average distribution. The single exception was associated with the broad log-normal VA/Q distribution, which is rarely observed using the technique. We conclude that the VA/Q distribution conventionally recovered approximates a simple average of all compatible distributions. It therefore displays average features and only that degree of fine structural detail that is typical of the family as a whole.     

Formation of cellobiose lipids by growing and resting cells of Ustilago maydis

Summary Utilizing coconut oilUstilago maydis ATCC 14826 synthesizes cellobiose lipids under N-limitation conditions and as resting cells, which gave the highest specific biosurfactant production (0.79 g/g substrate). C6-, C12-, C14-, and 15, 16-dihydroxy-C16-fatty acids are the main components of the lipophilic moiety of these glycolipids.     

Polyamine depletion increases cellular ribonucleotide levels

Summary Depletion of the putrescine and spermidine content of Ehrlich ascites tumor cells by -difluoromethylornithine (DFMO) treatment results in at least a 1500-fold increase in the decarboxylated S-adenosylmethionine (deSAM) content. The accumulation of this adenine nucleoside occurs because of the absence of putrescine and spermidine to act as aminopropyl group acceptors in the spermidine and spermine synthase reactions and because of an increase in S-adenosylmethionine decarboxylase activity. The fact that the synthesis of deSAM continues in DFMO-treated cells makes the pathway an adenine trap. This prompted a study of the adenine nucleotide pools. High-performance liquid chromatographic analysis showed that the total adenine nucleotide pool increased, rather than decreased, as a result of DFMO treatment; the major contributors to the increase being ATP and ADP, which increased 2.6 and 1.9 times, respectively. The cellular content of other ribonucleotides increased as well, particularly that of UTP and CTP. When putrescine was added together with DFMO, the increases in cellular ribonucleotide contents were prevented, showing that they were indeed caused by polyamine depletion.     

Nuclease recognition of an alternating structure in a d(AT)14 plasmid insert.

The nuclease reactivity and specificity of a cloned tract of poly X (dA-dT) X poly(dA-dT) has been explored. Digestion with DNAse I, Mung Bean nuclease, S1 nuclease, DNAse II, and copper (1,10-phenanthroline)2 on a 256 base pair restriction fragment containing d(AT)14A revealed a dinucleotide repeat structure for the alternating sequence. Furthermore, conditions which wind or unwind the linear DNA had little effect on the reactivity of the AT insert. These preferred cleavages offer insights to structural alterations within the DNA helix which differ from A, B, or Z-DNA. Nucleation into flanking sequences by this structural alteration was not observed.