| 1. |
- Thomas, C M, et al.
(author)
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Regulation of replication and maintenance functions of broad host-range plasmid RK2.
- 1985
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In: Basic life sciences. - 0090-5542. ; 30
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Journal article (peer-reviewed)abstract
- Replication of broad host-range plasmid RK2 depends on a cisacting vegatative replication origin oriVRK2 and the polypeptide product(s) of the trans-acting gene trfA as well as on host-specified products. The trfA gene is the second cistron in a polycistronic unit whose first cistron may be kilD, one of 4 known RK2-specified kil loci (kilA, B, C, and D) which are inhibitory for bacterial host or plasmid vector in the absence of kor functions which suppress in trans the effect of their respective kil genes. Transcription of the operon containing trfA is negatively regulated by the products of both the trfB locus (alias korD and korA) and korB. The loci, trfB and korB, are expressed from a single transcriptional unit which we propose to be negatively autoregulated by the products of both loci, although an additional, weaker and unregulated transcript may also express korB. While deletions in the oriVRK2 region have indicated the presence of copy number control elements adjacent to and possibly overlapping with the minimal oriVRK2 segment, the overriding control of copy number seems to reside in the trfB and korB loci which in conjunction appear to reduce expression of the trfA gene to levels limiting for replication. Coregulation of trfA with kil genes may indicate that kil genes play a role in plasmid maintenance other than replication.
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| 2. |
- Li, C-H., et al.
(author)
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A lattice resolution study of the martensitic transformation of small iron particles in a copper matrix
- 1985
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In: Acta Metallurgica. - : Elsevier BV. - 0001-6160. ; 33:2, s. 317-328
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Journal article (peer-reviewed)abstract
- The martensitic transformation of small, fully coherent, gamma iron precipitates in an epsilon copper matrix, brought about by the bombardment of thin foils with argon ions, has been studied using lattice fringe imaging. It is found, in general, that only partial transformation of individual particles occurs, this corresponding to a simple homogeneous shear (a Bain strain). In addition, the transformation is limited to particles located within about two particle diameters of the foil surface. It is established that the mere presence of a Frank (or Shockley) loop in a particle, due to the bombardment, is insufficient to trigger the transformation. The implications of this result are discussed with reference to bulk martensite. In the present case, it is concluded that transformation may simply initiate at sites of local decohesion or microslip at the matrix/particle boundaries brought about by vacancy condensation following ion bombardment, these sites being most effective in the vicinity of free surfaces
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| 3. |
- Lopez-Rivas, Abelardo, et al.
(author)
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Ca2+-mobilizing actions of platelet-derived growth factor differ from those of bombesin and vasopressin in Swiss 3T3 mouse cells
- 1987
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In: Proceedings of the National Academy of Sciences of the United States of America. - : The National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 84:16, s. 5768-5772
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Journal article (peer-reviewed)abstract
- Addition of the mitogenic peptides bombesin and vasopressin to quiescent Swiss 3T3 mouse cells increased the cytosolic Ca2+ concentration without any measurable delay. In contrast, there was a significant lag period (16 +/- 1.2 s) before platelet-derived growth factor (PDGF) increased cytosolic Ca2+ concentration. This lag was not diminished at high concentrations of either porcine or human PDGF. Similar results were obtained in 3T3 cells loaded with quin-2 or fura-2. The differences in the effects of bombesin, vasopressin, and PDGF on Ca2+ movements were also substantiated by measurements of 45Ca2+ efflux and of cellular 45Ca2+ content. Activation of protein kinase C by phorbol esters inhibited Ca2+ mobilization induced by either bombesin or vasopressin. In contrast, phorbol esters had no effect on PDGF-induced cytosolic Ca2+ concentration increase or acceleration of 45Ca2+ efflux. Finally, bombesin and vasopressin caused a rapid increase in the production of inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate, whereas PDGF, even at a saturating concentration, exerted only a small effect. These results indicate that the signal transduction pathways activated by PDGF that lead to Ca2+ mobilization can be distinguished from those utilized by bombesin and vasopressin.
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| 4. |
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| 5. |
- Smith, S M, et al.
(author)
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Role of neutrophils in hemorrhagic shock-induced gastric mucosal injury in the rat
- 1987
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In: Gastroenterology. - 0016-5085 .- 1528-0012. ; 93:3, s. 466-471
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Journal article (peer-reviewed)abstract
- Gastric mucosal clearance of 51Cr-labeled red blood cells (51Cr-RBC) was measured in rats during a 30-min control period, a 30-min ischemic period (hemorrhage to 27 mmHg arterial pressure), and a 60-min reperfusion period (reinfusion of shed blood). In untreated (control) rats, a dramatic rise in the leakage of 51Cr-labeled red blood cells into the gastric lumen was observed during the reperfusion period. Treatment with neutrophil antiserum attenuated 51Cr-labeled red blood cell flux into the gastric lumen. Using the radioactive microsphere technique, neutrophil-depleted animals were shown to have higher blood flows in the ischemic period than the untreated rats. Bleeding of untreated rats to a mean arterial pressure of 40 mmHg resulted in blood flows that were not different from those in antiserum-treated rats bled to 27 mmHg and leakage of 51Cr-labeled red blood cells similar to that measured in antiserum-treated rats. The results of this study indicate that neutrophils play an important role in hemorrhagic shock-induced gastric bleeding.
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