Recovery of radial PO(2) profiles from phosphorescence quenching measurements in microvessels

Work by previous investigators has indicated that a substantial amount of oxygen diffuses from the precapillary circulation. These losses imply that there should be radial gradients of oxygen tension (PO(2)) in arterioles, leading to a non-uniform distribution of oxygen within these microvessels. We have employed the phosphorescence quenching method to measure oxygen, allowing us to evaluate the heterogeneity of PO(2) inside short segments of microvessels. The phosphorescence decay curve contains information about the distribution of oxygen within the excited volume and the distribution can be represented as a histogram, by decomposing the decay curve into several components with weights proportional to the volume fraction of plasma with different PO(2), under the condition of a high signal-to-noise ratio. Furthermore, the histogram can be converted into a radial profile of PO(2), based on the assumptions of a circular vascular lumen, axisymmetric distribution of oxygen and monotonic PO(2) profile. Albumin-bound Pd-porphyrin phosphor was infused into the circulation of hamsters and excited by flash illumination at 10 Hz, with a square region of excitation light just covering the entire lumen, (i.e. width of region equaled luminal diameter) of microvessels in the hamster mesentery. A set of 50 curves (5 s of data) was averaged to obtain a decay curve with low noise. Curves were analyzed with the above histogram procedure, and this analysis allowed us to distinguish between PO(2) values originating from intra and extravascular subvolumes. The intravascular PO(2) in these microvessels was very heterogeneous, which could be explained by the existence of significant radial PO(2) gradients. The radial PO(2) gradients were estimated to be approximately 1 mmHg/microm.     

Interaction of human rad51 recombination protein with single-stranded DNA binding protein, RPA.

Replication protein A (RPA), a heterotrimeric single-stranded DNA binding protein, is required for recombination, and stimulates homologous pairing and DNA strand exchange promoted in vitro by human recombination protein HsRad51. Co-immunoprecipitation revealed that purified RPA interacts physically with HsRad51, as well as with HsDmc1, the homolog that is expressed specifically in meiosis. The interaction with HsRad51 was mediated by the 70 kDa subunit of RPA, and according to experiments with deletion mutants, this interaction required amino acid residues 169-326. In exponentially growing mammalian cells, 22% of nuclei showed foci of RPA protein and 1-2% showed foci of Rad51. After gamma-irradiation, the percentage of cells with RPA foci increased to approximately 50%, and those with Rad51 foci to 30%. All of the cells with foci of Rad51 had foci of RPA, and in those cells the two proteins co-localized in a high fraction of foci. The interactions of human RPA with Rad51, replication proteins and DNA are suited to the linking of recombination to replication.     

ClassAsteretea tripolium on the territory of the former USSR and Mongolia

Higher syntaxa of the classAsteretea tripolium are reviewed. This class covers plant communities of the Euro-Asian continent on low- and medium-salinized soils with medium moisture conditions where perennial herbaceous plants (hemicryptophytes) of non-succulent character prevail. On the territory of the former USSR and Mongolia, the classAsteretea tripolium is represented by the following orders:Glauco-Puccinellietalia Beeftink etWesthoff inBeeftink 1962,Cirsietalia esculenti Mirkin etV. Golub exV. Golub ord. novus,Scorzonero-Juncetalia gerardii Vicherek 1973,Halerpestetalia Mirkin et al. exV. Golub ord. novus,Artemisio santonicae-Limonietalia gmelinii V. Golub etV. Solomakha 1988,Suaedetalia corniculatae V. Golub ord. novus. Superspecies and aggregations of species are used for the diagnosis of higher syntaxa.     

Transposon-mediated insertion of R factor into bacterial chromosome

Summary Insertion of transposon Tn1 into the E. coli JC411 chromosome results in a sharp increase of plasmid RP4 integration frequency. This effect is absent in JC1553 recA cells. The RP4 integration with the chromosome is probably accomplished via recA-dependent recombination between transposon Tn1 inserted into the chromosome and the same transposon in the RP4 plasmid.     

In vitro sensitization of human lymphoid cells to antigens on cultured melanoma cells. I. Culture conditions resulting in augmented cell-mediated cytotoxicity

Culture conditions have been established that result in the sensitization of normal human peripheral blood lymphoid cells on allogeneic melanoma monolayers. Optimal culture conditions require 2 to 8 × 10⁶ mitomycin C treated stimulator melanoma cells to sensitize 5 to 10 × 10⁶ responder lymphoid cells. Neither rocking nor refeeding of the culture is necessary for the sensitization procedure. Stimulator cells grown in either fetal calf serum or human serum will serve as effective stimulator or target cells. Peak cytotoxic activity was detected at 44 hr in a microcytotoxicity assay, although some cytotoxic activity was detectable at 24 hr.     

Leukemia in AKR mice: III. Size distribution of suppressor T-cells in AKR leukemia and neonatal mice

Suppression of in vitro antibody forming potential of normal cells by leukemic cells of AKR and normal neonatal mice have many similarities. In both cases the suppression is by cell contact rather than by the elaboration of soluble suppressive factors and the suppression is sensitive to both x-irradiation and mitomycin C treatment. When the size distribution of suppressing cells in thymus and spleen were compared by velocity sedimentation, both leukemic and neonatal suppressing cells had similar size distribution in each organ. Both large and small cells in the thymus suppress but only large cells (sedimentation velocity >3.5 mm/hr) in the spleen are able to suppress. Leukemic cells in lymph node have a splenic size distribution, viz., only large cells suppress. Both large and small cells of a subcutaneously growing long passage AKR lymphoma are able to suppress. While large cells contain the bulk of cells actively incorporating tritiated thymidine and thus probably in cycle, small but significant amounts of incorporation in small suppressing cells is also seen.     

The effect of age and 1,25-dihydroxyvitamin D3 treatment on the intestinal calcium-binding protein of suckling rats.

The intestinal level of the vitamin D-dependent duodenal calcium-binding protein was assayed by an equilibrated column technique in rat embryos, neonates, and pups. Calcium-binding protein was undetectable in unborn, newborn, and 1- to 2-day-old rats i.e., the level was lower than in severely vitamin D-deficient animals. Calcium-binding protein was detected after the animals were 5-days old and thereafter rose monotonically as a function of body weight. Treatment with 1,25-dihydroxyvitamin D₃ failed to raise the calcium-binding protein levels of newborn or 1-day-old rats, but doubled the level in 11- or 12-day-old pups. Plasma calcium was raised in all treated animals. The failure to detect calcium-binding protein in vitamin D-replete suckling animals provides evidence for a dissociation between calcium absorption and calcium binding protein.