What are mycoplasmas: the relationship of tempo and mode in bacterial evolution

In phenotype the mycoplasmas are very different from ordinary bacteria. However, genotypically (i.e., phylogenetically) they are not. On the basis of ribosomal RNA homologies the mycoplasmas belong with the clostridia, and indeed have specific clostridial relatives. Mycoplasmas are, however, unlike almost all other bacteria in the evolutionary characteristics of their ribosomal RNAs. These RNAs contain relatively few of the highly conserved oligonucleotide sequences characteristic of normal eubacterial ribosomal RNAs. This is interpreted to be a reflection of an elevated mutation rate in mycoplasma lines of descent. A general consequence of this would be that the variation associated with a mycoplasma population is augmented both in number and kind, which in turn would lead to an unusual evolutionary course, one unique in all respects. Mycoplasmas, then, are actually tachytelic bacteria. The unusual evolutionary characteristics of their ribosomal RNAs are the imprints of their rapid evolution.     

Changes in viscoelastic properties of rat lung parenchymal strips with maturation.

The lung extracellular matrix changes rapidly with maturation. To further our understanding of the mechanisms underlying lung tissue mechanics, we studied age-related changes in mechanical properties in lung parenchymal strips from baby (10-15 days old), young ( approximately 3 wk old), and adult ( approximately 8 wk old) rats. Subpleural strips were cut and suspended in a fluid-filled organ bath. One end of the strip was attached to a force transducer and the other to a servo-controlled lever arm. Measurements of force (F) and length (L) were recorded during sinusoidal oscillations of various amplitudes and frequencies. Resistance modulus (R) and elastance modulus (E) were estimated by fitting the equation of motion to changes in stress (T) and stretch ratio (lambda). Hysteresivity (eta) was calculated as follows: eta = (R/E)2pif, where f is frequency. Slow-cycling T-lambda curves were measured by applying a constant slow length change. Finally, quasi-static T-lambda curves were measured as stress was increased from 0 to 6 kPa and back to 0 kPa in stepwise increments. Our results showed that lung tissue from immature rats was stiffer and less hysteretic than tissue from more mature animals. In addition, tissue from baby animals behaved in a manner compatible with an increased vulnerability to plastic change.     

Subunit II of cytochrome c oxidase from Paracoccus denitrificans. DNA sequence, gene expression and the protein

Cytochrome c oxidase from the bacterium Paracoccus denitrificans, while being related to the mitochondrial enzyme in many ways, consists of only two to three different subunits. For the identification of its genes, a Paracoccus DNA library was constructed and screened with specific antibodies for expression of cloned inserts in E. coli. A positive clone expressing immunoreactive products in the molecular mass region of authentic subunit II revealed a high homology of its DNA-deduced amino acid sequence with subunit II sequences of the mitochondrial oxidases; several typical features, such as the transmembrane folding pattern and the presumed copper-binding site, are highly conserved between prokaryotic and mitochondrial polypeptides. A comparison with peptide sequencing data of the purified subunit established the presence of a characteristic N-terminal extension as well as a longer C terminus in the initial translation product of the Paracoccus subunit; by mass spectroscopy, the first N-terminally blocked residue of the mature polypeptide was identified as a pyroglutamate. No code abnormalities, but a highly specific codon usage were observed; no evidence for a localization of the subunit I gene directly adjacent to this gene has been obtained.     

Rhizobium sp. strain ORS571 grows synergistically on N2 and nicotinate as N sources.

Rhizobium sp. strain ORS571 conducts synergistic, free-living N2 fixation and nicotinate oxidation. Explicitly, ORS571 is able to fix N2 aerobically because 6-OH-nicotinate acts as an intracellular O2 sink. Because 6-OH-nicotinate oxidation is mandatory for aerobic, free-living N2 fixation and because the synergistic processes yield ammonium from substrates (as the nitrogen source for growth), ORS571 is not a diazotroph.     

What are mycoplasmas: The relationship of tempo and mode in bacterial evolution

Summary In phenotype the mycoplasmas are very different from ordinary bacteria. However, genotypically (i.e., phylogenetically) they are not. On the basis of ribosomal RNA homologies the mycoplasmas belong with the clostridia, and indeed havespecific clostridial relatives. Mycoplasmas are, however, unlike almost all other bacteria in the evolutionary characteristics of their ribosomal RNAs. These RNAs contain relatively few of the highly conserved oligonucleotide sequences characteristic of normal eubacterial ribosomal RNAs. This is interpreted to be a reflection of an elevated mutation rate in mycoplasma lines of descent. A general consequence of this would be that the variation associated with a mycoplasma population is augmented both in number and kind, which in turn would lead to an unusual evolutionary course, one unique in all respects. Mycoplasmas, then, are actually tachytelic bacteria. The unusual evolutionary characteristics of their ribosomal RNAs are the imprints of their rapid evolution.     

Partitioning of pulmonary resistance during constriction in the dog: effects of volume history

We assessed the relative changes in airways and lung tissue with bronchoconstriction, and the changes in each during and following a deep inhalation (DI). We partitioned pulmonary resistance (RL) into airway (Raw) and tissue (Vtis) components using alveolar capsules in 10 anesthetized, paralyzed, and open-chested dogs ventilated sinusoidally with 350-ml breaths at 1 Hz. We made measurements before and during bronchoconstriction induced by vagal stimulation or inhalation of histamine or prostaglandin F2 alpha (PGF2 alpha), each of which decreased dynamic compliance by approximately 40%. With histamine and PGF2 alpha the rise in RL was predominantly due to Vtis. With vagal stimulation there was a relatively greater increase in Raw than Vtis. At higher lung volumes, Vtis increases offset falls in Raw, producing higher RL at these volumes before and during constriction with PGF2 alpha and histamine. During constriction with vagal stimulation, the fall in Raw with inflation overrode the rise in Vtis, resulting in a lower RL at the higher compared with the lower lung volume. The changes seen after a DI in the control and constricted states were due to alterations in tissue properties, both viscous and elastic. However, the relative hysteresis of the airways and parenchyma were equal, since Raw, our index of airway size, was unchanged after a DI.     

Use of monoclonal antibodies as a diagnostic tool in human leukemia. I. Acute myeloid leukemia and acute phase of chronic myeloid leukemia

Various monoclonal antibodies (mAbs) detecting certain different epitopes on myeloid cells (VIMD5, D5 D6, OKM1, Leu-M3, VIEG4, OKIa 1) have been used in combination with conventional markers (antihuman myeloid hetero-antiserum, FcIgG-receptors, C3d-receptors) to further define the phenotypic heterogeneity of myeloid leukemia. Subsequent leukemic samples from previously untreated patients with acute myeloid leukemia (AML) (51 adults, 24 children) and from nine adult patients in the acute phase of chronic myeloid leukemia (CML-BC) were studied. It was possible to demonstrate quantitative differences in the expression of antigens on the various leukemia subtypes which could be exploited for diagnosis. Furthermore our results revealed that there is a very close correlation between the different surface phenotypes and the types morphologically assessed according to FAB-criteria.