Characterization of two new plasmid DNAs found in mitochondria of wild-type Neurospora intermedia strains

Mitochondria from two Neurospora intermedia strains (P4O5-Labelle and Fiji N6-6) were found to contain plasmid DNAs in addition to the standard mitochondrial DNA species. The plasmid DNAs consist of monomeric circles (4.1-4.3 kbp and 5.2-5.3 kbp for Labelle and Fiji, respectively) and oligomers in which monomers are organized as head-to-tail repeats. DNA-DNA hybridization experiments showed that the plasmids have no substantial sequence homology to mtDNA, to each other, or to a previously characterized mitochondrial plasmid from N. crassa strain Mauriceville-lc (Collins et al. Cell 24, 443-452, 1981). The intramitochondrial location of the plasmids was established by cell fractionation and nuclease protection experiments. In sexual crosses, the plasmids showed strict maternal inheritance, the same as Neurospora mitochondrial DNA. The plasmids may represent a novel class of mitochondrial genetic elements.     

The nucleotide sequence coding for major outer membrane protein OmpA of Shigella dysenteriae.

The nucleotide sequence of the ompA gene from Shigella dysenteriae has been determined and the amino acid sequence of the pro-OmpA protein predicted. Sequence comparison between the ompA genes of S.dysenteriae and Escherichia coli showed that features such as mRNA secondary structure and codon usage, as well as polypeptide function, have been conserved during evolution. The pro-OmpA protein of S.dysenteriae consists of 351 residues, as opposed to the 346 of the E.coli protein and also shows several amino acid changes. These changes have been used to interpret differences in the biological activity of the two proteins.     

Segmental flexibility of ribosomal protein S1 bound to ribosomes and Q beta-replicase

The protonization pattern of the endogenous donor component D₁ which feeds electrons directly into chl-a⁺_II has been analyzed in Tris-washed inside-out thylakoids with the aid of appropriate pH-indicators. It was found that under repetitive flash excitation the amount of protons released is proportional to the extent of D₁-oxidation, depending on the time between the flashes. The kinetics of D₁-oxidation (being practically the same as in normal Tris-washed chloroplasts) are faster than the proton release by two orders of magnitude. The results lead to the conclusion that D₁ is protonized in the reduced state with pK(D^ox₁) < 5 and becomes deprotonized in the oxidized state with pK(D^red₁) ? 8. The proton release is kinetically limited by a transport barrier. Implications on the interpretation of the proton release pattern in preparation with intact water oxidation are discussed.     

Blood carboxyhaemoglobin,plasma thiocyanate,and cigarette consumption: implications for epidemiological studies in smokers.

Carboxyhaemoglobin and plasma thiocyanate concentrations were found to be significantly correlated with self-reported daily cigarette consumption in 360 smokers (r = 0.416 and 0.412 respectively; p less than 0.001). The extent to which inhalation patterns affected the intake of cigarette smoke constituents was determined from the partial correlation between carboxyhaemoglobin and plasma thiocyanate concentrations after the number of cigarettes smoke per day had been allowed for (r = 0.48). Thus 23% of the variation in carboxyhaemoglobin and thiocyanate concentrations was accounted for by the was a cigarette was smoked and a further 21% by the number smoked a day. Furthermore, the relation between carboxyhaemoglobin or plasma thiocyanate and daily cigarette consumption was not linear but reached an asymptote at consumption rates above 25 cigarettes a day. These results suggest that by itself daily cigarette consumption will not identify those smokers most at risk and will also underestimate and dose-response relationship between smoking and selected diseases.     

Mapping,quantitative distribution and origin of substance P- and VIP-containing nerves in the Uvea of guinea pig eye

Summary VIP- and substance P-like immunoreactivities were found in considerable concentrations (VIP: 17.3±4.8 pmol/g, mean ± SEM; substance P:11.1±1.8 pmol/g) in the uveal portion of the guinea pig eye.d Immunocytochemistry localised these two regulatory peptides to nerve fibres found principally in a plexus in the iris (substance P) and in an extensive network surrounding the blood vessels of the choroid (VIP). A remarkable anatomical demarcation of the two types of peptide-containing nerves was established by the staining of substance P-containing nerves, which stops at the level of the ciliary body. This uveal area is known to be involved in the ocular responses to nociceptive stimuli. At the ultrastructural level, immunoreactivity for both peptides was localised to distinct subpopulations of p-type nerves, distinguishable by the size of their large dense-cored vesicles. Those immunoreactive for VIP were significantly larger (p<0.0005) than those immunoreactive for substance P (95±7 nm and 82±9 nm respectively; mean ± SD). Interruption of the trigeminal pathway produced a remarkable decrease of substance P immunoreactivity in the anterior portion of the uvea (9.1±1.5 pmol/g, mean ± SEM, control; 5.3±1.3 pmol/g, denervated), but not of VIP immunoreactivity in the choroid. Following colchicine treatment, VIP-immunoreactive neuronal cell bodies were localised in the choroid. The separate anatomical localisations and distributions of the two uveal peptides appear to be related to their different origins and functional roles in the response of the eye to noxious stimuli.To whom offprint requests should be sent     

A test for hormonal responsiveness in a mammary epithelial cell line,NMuMg

Summary The NMuMG cell line derived from normal mouse mammary epithelial cells was tested for responsiveness to hormones. The hormones studied included insulin, glucocorticoids (cortisol and dexamethasone), and prolactin. In addition to membrane bound insulin receptors and prolactin receptors, the cells had 2 × 10⁴ cytoplasmic glucocorticoid receptors per cell. Morphological changes were observed in response to hormones. Clusters of cells appeared with greatly increased diameter, and the number of cells per plate was reduced. The rate of DNA synthesis, corrected by cell number, indicates that cell division, and hence cell turnover, was increased by the combination of all three hormones. Insulin greatly enhanced protein synthesis, but glucocorticoid and prolactin did not further increase the rate. The combination of the three hormones produced a change in the synthesis of histones, consistent with the increase in cell turnover. There were substantial responses of enzyme activities to hormonal treatment of the cells. Insulin by itself induced a doubling of the activity of glyceraldehyde phosphate dehydrogenase and perhaps a modest increase in NADH-cytochromec reductase. Lactose synthetase activity showed a three- to fourfold induction of both A and B subunits of the enzyme when the cells were treated with insulin, glucocorticoid, and prolactin, and the effect of the latter two hormones was shown to be additional to that of insulin. This work was supported by Contract N01-CB-43866 from the National Cancer Institute, by Grants GB-38658 from the National Science Foundation and GMS-20338 from the National Institutes of Health, and by the Agricultural Experimental Station at the University of California.     

The mutagenic potency of 1,8-dinitropyrene in cultured mouse lymphoma cells

Although non-toxic, 1,8-dinitropyrene (1,8-DNP) was mutagenic for mouse lymphoma L5178Y cells when assayed for induced resistance to 6-thioguanine, methotrexate, ouabain and 1-β-D-arabinofuranosyl cytosine. In bacteria, nitropyrenes are potent inducers of frame-shift mutations, and the induction of ouabain-resistant mutants, believed to be due to base-pair substitutions, suggests that the mechanism of action may be different in mouse cells and bacteria. Long treatment times were required to detect 1,8-DNP-induced mutants in L5178Y cells, suggesting the possibility of an inducible activation system. 4-Nitroquinoline 1-oxide was both toxic and mutagenic to these same 4 mutation assays after short (2 h) treatment times. The dilemma that exists when comparing the mutagenic potential of test chemicals when concentration of mutagen, treatment times and toxicity are markedly different, is discussed.